Net-like structure

ABSTRACT

A net-like structure has a three-dimensional random loop bonded structure constituted of a thermoplastic elastomer continuous linear body having a fiber size of greater than or equal to 0.1 mm and less than or equal to 3.0 mm. The net-like structure has, in the thickness direction, a solid-section fiber main region mainly including solid-section fibers, a hollow-section fiber main region mainly including hollow-section fibers, and a mixed region including solid-section fibers and hollow-section fibers in a mixed state, located between the solid-section fiber main region and the hollow-section fiber main region. Both solid-section fiber main region-side residual strain of the net-like structure and hollow-section fiber main region-side residual strain of the net-like structure are less than or equal to 20%, and the difference between the solid-section fiber main region-side residual strain and the hollow-section fiber main region-side residual strain is less than or equal to 10 points.

TECHNICAL FIELD

The present invention relates to a net-like structure suitable for anet-like cushion material used for office chairs, furniture, sofas,beddings such as beds, seats for vehicles such as trains, automobiles,two-wheeled vehicles, baby buggies, child safety seats, and wheelchairs,and shock-absorbing mats such as floor mats and members for preventingcollision and nipping, etc.

BACKGROUND ART

At present, as a cushion material used for furniture, beddings such asbeds, and seats for vehicles such as trains, automobiles, andtwo-wheeled vehicles, a net-like structure is increasingly used.Japanese Patent Laying-Open No. H7-68061 (PTD 1) and Japanese PatentLaying-Open No. 2004-244740 (PTD 2) disclose methods for manufacturing anet-like structure. Net-like structures have merits, compared withfoamed-crosslinked urethane, of having a comparable level of durability,being excellent in moisture and water permeability and air permeability,and being low in heat storage properties and therefore providingresistance against stuffiness. Moreover, net-like structures, made ofthermoplastic resin, have other advantages of being easy in recycling,having no worry about residual agents, and being environmentallyfriendly. However, in these net-like structures, with some exceptions,there has been no concept of differentiating the front from the back,with the same cushioning feeling given whichever face is used.

A net-like structure has unique cushioning performance, but has founddifficulty in changing the cushioning performance by itself. To addressthis problem, Japanese Patent Laying-Open No. H7-189105 (PTD 3)discloses a different-fineness net-like structure and a method formanufacturing the same. This structure is constituted of a base layerresponsible for vibration absorption and retention of body shape and asurface layer responsible for properties of being soft and ensuringuniform pressure dispersion. In this way, the layers play differentroles, aiming to improve comfort to sit on when the user sits from theside of the surface layer. However, no consideration has been made foruse of sitting from both sides, from the side of the surface layer andfrom the side of the base layer. Compression durability is lower in thecase of sitting from the side of the surface layer than in the case ofsitting from the side of the base layer: i.e., compression durability isdifferent between the case of sitting from the side of the surface layerand the case of sitting from the side of the base layer.

Net-like structures having different designs may be bonded together byadhesion, bound with a band, or integrated with a side cloth. This hashowever problems that the production cost is high and that thecushioning feeling may change by using an adhesive, causing a feeling ofstrangeness. In addition, there has been a problem that compressiondurability is greatly different between both faces.

CITATION LIST Patent Document

PTD 1: Japanese Patent Laying-Open No. H7-68061

PTD 2: Japanese Patent Laying-Open No. 2004-244740

PTD 3: Japanese Patent Laying-Open No. H7-189105

SUMMARY OF INVENTION Technical Problems

In view of the problems of the background art described above, an objectof the present invention is providing a net-like structure capable ofimparting cushioning performance different between both faces, andhaving an effect that the difference in compression durability is smallfrom whichever face pressure is applied.

Solutions to Problems

After having devoted themselves to researches for solving the aboveproblems, the present inventors have finally completed the presentinvention, which includes the followings.

[1] net-like structure having a three-dimensional random loop bondedstructure constituted of a thermoplastic elastomer continuous linearbody that is either a polyester-based thermoplastic elastomer continuouslinear body or a polyolefin-based thermoplastic elastomer continuouslinear body having a fiber size of greater than or equal to 0.1 mm andless than or equal to 3.0 mm, wherein the net-like structure has, in athickness direction of the net-like structure, a solid-section fibermain region mainly including fibers having a solid cross section, ahollow-section fiber main region mainly including fibers having a hollowcross section, and a mixed region including fibers having a solid crosssection and fibers having a hollow cross section in a mixed state,located between the solid-section fiber main region and thehollow-section fiber main region, both solid-section fiber mainregion-side residual strain after 750 N constant load repeatedcompression at pressurization from the side of the solid-section fibermain region of the net-like structure and hollow-section fiber mainregion-side residual strain after 750 N constant load repeatedcompression at pressurization from the side of the hollow-section fibermain region of the net-like structure are less than or equal to 20%, anda difference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain isless than or equal to 10 points. The fiber size as used herein refers toan average fiber size of a plurality of measured values as will bedescribed later on a measuring method.

[2] The net-like structure according to [1], wherein an apparent densityis greater than or equal to 0.005 g/cm³ and less than or equal to 0.20g/cm³.

[3] The net-like structure according to [1] or [2], wherein the fibershaving a hollow cross section have a fiber size greater than the fibershaving a solid cross section, and a difference in fiber size between thefibers having a solid cross section and the fibers having a hollow crosssection is greater than or equal to 0.07 mm. The difference in fibersize as used herein refers to a difference between an average fiber sizeof the fibers having a solid cross section and an average fiber size ofthe fibers having a hollow cross section.

[4] The net-like structure according to any of [1] to [3], wherein aratio between 25% compression hardness at pressurization from the sideof the solid-section fiber main region and 25% compression hardness atpressurization from the side of the hollow-section fiber main region isgreater than or equal to 1.03.

[5] The net-like structure according to any of [1] to [4], wherein aratio between 40% compression hardness at pressurization from the sideof the solid-section fiber main region and 40% compression hardness atpressurization from the side of the hollow-section fiber main region isgreater than or equal to 1.05.

[6] The net-like structure according to any of [1] to [5], wherein adifference between a compression deflection coefficient atpressurization from the side of the solid-section fiber main region anda compression deflection coefficient at pressurization from the side ofthe hollow-section fiber main region is less than or equal to 5.

[7] The net-like structure according to any of [1] to [6], wherein adifference between a hysteresis loss at pressurization from the side ofthe solid-section fiber main region and a hysteresis loss atpressurization from the side of the hollow-section fiber main region isless than or equal to 5 points.

[8] The net-like structure according to any of [1] to [7], wherein thethermoplastic elastomer continuous linear body is the polyester-basedthermoplastic elastomer continuous linear body, and both a hysteresisloss at pressurization from the side of the solid-section fiber mainregion and a hysteresis loss at pressurization from the side of thehollow-section fiber main region are less than or equal to 30%.

[9] The net-like structure according to any of [1] to [7], wherein thethermoplastic elastomer continuous linear body is the polyolefin-basedthermoplastic elastomer continuous linear body, and both a hysteresisloss at pressurization from the side of the solid-section fiber mainregion and a hysteresis loss at pressurization from the side of thehollow-section fiber main region are less than or equal to 60%.

[10] A cushion material including the net-like structure according toany of [1] to [9] inside the cushion, wherein the cushion material isusable reversibly.

Advantageous Effects of Invention

The net-like structure of the present invention is a net-like structurehaving cushioning performance different between the front and back facesof the net-like structure and having an effect that the difference incompression durability is small from whichever face, the front or backface, pressure is applied. This has made it possible to provide anet-like structure that is usable reversibly and suitably used foroffice chairs, furniture, sofas, beddings such as beds, seats forvehicles such as trains, automobiles, and two-wheeled vehicles, etc. Anexample of the effect of being usable reversibly is an effect that acushion material having the following features can be provided: i.e., insummer, the side of fibers having a hollow cross section, which has athick fiber size, may be used as the front face, whereby a comparativelyhard cushioning feeling and reduction in contact area make the user feelcool, and in winter, the side of fibers having a solid cross section,which has a thin fiber size, may be used as the front face, whereby acomparatively soft cushioning feeling and increase in contact area makethe user feel warm.

Also, when the side of thin-size fibers having a solid cross section isused as the front face, the net-like structure of the present inventionis superior in compression durability to a net-like structureconstituted 100% of thin-size fibers having a solid cross section.Therefore, the net-like structure of the invention can be used desirablyeven when the side of thin-size fibers having a solid cross section isused as the front face, because compression durability is excellentcompared with the conventional product.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic graph showing a second stress-strain curve inhysteresis loss measurement of a net-like structure.

FIG. 1B is a schematic graph showing a stress-strain curve at secondcompression in hysteresis loss measurement of a net-like structure.

FIG. 1C is a schematic graph showing a stress-strain curve at seconddecompression in hysteresis loss measurement of a net-like structure.

DESCRIPTION OF EMBODIMENTS

The present invention will be described hereinafter in detail. Thepresent invention relates to a net-like structure having athree-dimensional random loop bonded structure constituted of athermoplastic elastomer continuous linear body that is either apolyester-based thermoplastic elastomer continuous linear body or apolyolefin-based thermoplastic elastomer continuous linear body having afiber size of greater than or equal to 0.1 mm and less than or equal to3.0 mm, wherein the net-like structure has, in a thickness direction ofthe net-like structure, a solid-section fiber main region mainlyincluding fibers having a solid cross section (hereinafter referred toas solid-section fibers), a hollow-section fiber main region mainlyincluding fibers having a hollow cross section (hereinafter referred toas hollow-section fibers), and a mixed region including solid-sectionfibers and hollow-section fibers in a mixed state, located between thesolid-section fiber main region and the hollow-section fiber mainregion, both solid-section fiber main region-side residual strain after750 N constant load repeated compression at pressurization from the sideof the solid-section fiber main region of the net-like structure andhollow-section fiber main region-side residual strain after 750 Nconstant load repeated compression at pressurization from the side ofthe hollow-section fiber main region of the net-like structure are lessthan or equal to 20%, and a difference between the solid-section fibermain region-side residual strain and the hollow-section fiber mainregion-side residual strain is less than or equal to 10 points.

The net-like structure of the present invention is a structure having athree-dimensional random loop bonded structure where a continuous linearbody constituted of a thermoplastic elastomer continuous linear bodythat is either a polyester-based thermoplastic elastomer or apolyolefin-based thermoplastic elastomer continuous linear body having afiber size of greater than or equal to 0.1 mm and less than or equal to3.0 mm is curled to form random loops and the loops are brought intocontact with one another in a molten state to be bonded together. Thethermoplastic elastomer continuous linear body according to the presentinvention is either a polyester-based thermoplastic elastomer or apolyolefin-based thermoplastic elastomer continuous linear body having afiber size of greater than or equal to 0.1 mm and less than or equal to3.0 mm.

Examples of the polyester-based thermoplastic elastomer include apolyester-ether block copolymer having thermoplastic polyester as hardsegments and polyalkylenediol as soft segments and a polyester blockcopolymer having aliphatic polyester as soft segments.

The polyester-ether block copolymer is a ternary block copolymerconstituted of: at least one kind of dicarboxylic acid selected fromaromatic dicarboxylic acids such as terephthalic acid, isophthalic acid,naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid,and diphenyl-4,4′-dicarboxylic acid, alicyclic dicarboxylic acids suchas 1,4-cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids suchas succinic acid, adipic acid, sebacic acid, and dimer acid, andester-forming derivatives thereof, etc.; at least one kind of diolcomponent selected from aliphatic diols such as 1,4-butanediol, ethyleneglycol, trimethylene glycol, tetramethylene glycol, pentamethyleneglycol, and hexamethylene glycol, alicyclic diols such as1,1-cyclohexanedimethanol and 1,4-cyclohexanedimethanol, andester-forming derivatives thereof, etc.; and at least one kind ofpolyalkylenediols such as polyethylene glycol having a number averagemolecular weight of about 300-5000, polypropylene glycol,polytetramethylene glycol, and glycol made of ethylene oxide-propyleneoxide copolymer.

The polyester block copolymer is a ternary block copolymer constitutedof: the dicarboxylic acid described above; the diol described above; andat least one kind of polyesterdiols such as polylactone having a numberaverage molecular weight of about 300-5000. Considering thermaladhesiveness, hydrolysis resistance, elasticity, heat resistance, etc.,especially preferred is a ternary block copolymer constituted ofterephthalic acid and/or naphthalene-2,6-dicarboxylic acid as thedicarboxylic acid, 1,4-butanediol as the diol component, andpolytetramethylene glycol as the polyalkylenediol, or a ternary blockcopolymer constituted of polylactone as the polyesterdiol. As a specialexample, one with polysiloxane-based soft segments introduced thereincan also be used.

As the polyester-based thermoplastic elastomer according to the presentinvention, the followings are also included: one with a non-elastomercomponent blended into, or copolymerized with, the above polyester-basedthermoplastic elastomer, one with a polyolefin-based component used assoft segments, etc. Also included are ones with various additives, etc.added to the polyester-based thermoplastic elastomer as required.

To achieve a net-like structure capable of imparting cushioningperformance different between both faces and having an effect that thedifference in compression durability is small from whichever facepressure is applied, which is an object of the present invention, thecontent of soft segments of the polyester-based thermoplastic elastomeris preferably greater than or equal to 15 wt %, more preferably greaterthan or equal to 25 wt %, even more preferably greater than or equal to30 wt %, especially preferably greater than or equal to 40 wt %, and,from the standpoint of secured hardness and heat and wear-and-tearresistance, it is preferably less than or equal to 80 wt %, morepreferably less than or equal to 70 wt %.

A component constituted of the polyester-based thermoplastic elastomerconstituting the net-like structure of the present invention preferablyhas an endothermic peak at a point less than or equal to a melting pointin a melting curve measured with a differential scanning typecalorimeter. The heat and wear-and-tear resistance significantlyimproves for one having an endothermic peak at a point less than orequal to the melting point, compared with one having no endothermicpeak. For example, as a preferred polyester-based thermoplasticelastomer according to the present invention, terephthalic acid,naphthalene-2,6-dicarboxylic acid, etc., which have rigidity, arecontained as an acid component of hard segments by greater than or equalto 90 mol %. More preferably, the content of terephthalic acid,naphthalene-2,6-dicarboxylic acid, etc. is greater than or equal to 95mol %, especially preferably, 100 mol %. Such terephthalic acid, etc.are transesterified with a glycol component and then polymerized to anecessary degree of polymerization. Thereafter, as a polyalkylenediol,polytetramethylene glycol having an average molecular weight ofpreferably greater than or equal to 500 and less than or equal to 5000,more preferably greater than or equal to 700 and less than or equal to3000, even more preferably greater than or equal to 800 and less than orequal to 1800 is copolymerized by preferably greater than or equal to 15wt % and less than or equal to 80 wt %, more preferably greater than orequal to 25 wt % and less than or equal to 70 wt %, even more preferablygreater than or equal to 30 wt % and less than or equal to 70 wt %,especially preferably greater than or equal to 40 wt % and less than orequal to 70 wt %. In this case, when the content of terephthalic acidand naphthalene-2,6-dicarboxylic acid, which have rigidity, as an acidcomponent of hard segments is large, the crystallinity of hard segmentsimproves, resisting plastic deformation, and improving heat andwear-and-tear resistance. The heat and wear-and-tear resistance will bemore improved when annealing treatment is further performed at atemperature less than the melting point by at least greater than orequal to 10° C. after heat melting adhesion. While the annealingtreatment is satisfactory by heating a sample at a temperature less thanthe melting point by at least greater than or equal to 10° C., the heatand wear-and-tear resistance will further improve by impartingcompression strain. When the thus-treated net-like structure is measuredwith a differential scanning type calorimeter, an endothermic peak isexhibited more clearly at a temperature greater than or equal to roomtemperature (e.g., 20° C.) and less than or equal to the melting pointin the melting curve. When no annealing is performed, an endothermicpeak is not exhibited clearly at a temperature greater than or equal toroom temperature (20° C.) and less than or equal to the melting point inthe melting curve. From this, it is considered that, by annealing, ametastable intermediate phase where the hard segments are rearranged isformed, whereby the heat and wear-and-tear resistance improves. Asusages of the heat resistance improving effect according to the presentinvention, applications in environments where the temperature may becomecomparatively high, such as cushions for vehicles where a heater is usedand flooring mats for heated floors, are useful because thewear-and-tear resistance becomes good.

The polyolefin-based thermoplastic elastomer according to the presentinvention is preferably an ethylene-α-olefin copolymer obtained bycopolymerizing ethylene and α-olefin, more preferably a multi-blockcopolymer constituted of ethylene-α-olefin that is an olefin blockcopolymer. The reason why a multi-block copolymer constituted ofethylene-α-olefin is more preferable is that, in a general randomcopolymer, the joining chain length of the main chain is short, makingit difficult to form a crystalline structure, which decreasesdurability. Preferably, α-olefin copolymerizing with ethylene isα-olefin having 3 or more carbons.

Examples of the α-olefin having 3 or more carbons include propylene,1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene,1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene,1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene,and 1-eicosene. Preferred are 1-butene, 1-pentene, 1-hexene,4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene,1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene,1-heptadecene, 1-octadecene, 1-nonadecene, and 1-eicosene. Also, two ormore kinds of them can be used.

The random copolymer that is the ethylene-α-olefin copolymer accordingto the present invention can be obtained by copolymerizing ethylene andα-olefin using a catalyst having a specific metallocene compound and anorganic metal compound as a basic configuration, and the multi-blockcopolymer can be obtained by copolymerizing ethylene and α-olefin usinga chain shuttling catalyst. As required, two or more kinds of polymerspolymerized by the above methods and polymers such as hydrogenatedpolybutadiene and hydrogenated polyisoprene can be blended.

The ratio between ethylene and α-olefin having 3 or more carbons in theethylene-α-olefin copolymer according to the present invention ispreferably greater than or equal to 70 mol % and less than or equal to95 mol % for ethylene and greater than or equal to 5 mol % and less thanor equal to 30 mol % for α-olefin having 3 or more carbons. In general,it is known that a macromolecular compound is provided with elastomericnature because hard segments and soft segments are present in amacromolecular chain. In the polyolefin-based thermoplastic elastomeraccording to the present invention, it is considered that ethylene playsa role of hard segments and α-olefin having 3 or more carbons plays arole of soft segments. Therefore, if the ratio of ethylene is less than70 mol %, hard segments will be small, reducing the recovery performanceof rubber elasticity. The ratio of ethylene is more preferably greaterthan or equal to 75 mol %, even more preferably greater than or equal to80 mol %. If the ratio of ethylene exceeds 95 mol %, soft segments willbe small, causing difficulty in exhibiting the elastomeric nature, andthus degrading cushioning performance. The ratio of ethylene is morepreferably less than or equal to 93 mol %, even more preferably lessthan or equal to 90 mol %.

In the net-like structure of the present invention, apart from thepolyester-based thermoplastic elastomer or the polyolefin-basedthermoplastic elastomer, a polymer modifier such as a styrene-isoprenecopolymer, a styrene-butadiene copolymer, and hydrogenated copolymersthereof, as a polybutadiene-based, polyisoprene-based, or styrene-basedthermoplastic elastomer, can be blended as a subsidiary material, asrequired. Moreover, the followings can be added: phthalate ester-based,trimellitate ester-based, aliphatic acid-based, epoxy-based, adipateester-based, and polyester-based plasticizers; known hinderedphenol-based, sulfur-based, phosphorous-based, and amine-basedantioxidants; hindered amine-based, triazole-based, benzophenone-based,benzoate-based, nickel-based, salicyl-based, and other lightstabilizers; antistatic agents; molecular weight modifiers such asperoxides; compounds having a reactive group such as epoxy-basedcompounds, isocyanate-based compounds, and carbodiimide-based compounds;metal deactivators; organic and inorganic nucleating agents;neutralizers; antacids; antimicrobial agents; fluorescent whiteners;fillers; flame retardants; flame retardant auxiliaries; and organic andinorganic pigments. It is also effective to increase the molecularweight of the polyolefin-based thermoplastic elastomer to improve heatresistance, durability, and wear-and-tear resistance.

One feature of the present invention is that cushioning performancedifferent between both faces can be imparted. A method for obtaining anet-like structure provided with cushioning performance differentbetween both faces is to allow the presence of the following regions atleast in the thickness direction of the net-like structure so as tochange the cushioning properties when the net-like structure iscompressed from each of the faces: i.e., a solid-section fiber mainregion mainly including solid-section fibers, by which its thickness isformed; a hollow-section fiber main region mainly includinghollow-section fibers, by which its thickness is formed; and a mixedregion other than the above regions, located between the solid-sectionfiber main region and the hollow-section fiber main region.

In the solid-section fiber main region and the hollow-section fiber mainregion, the wording “mainly” means that the percentage of the number offibers having the cross section in question in the total number offibers included in the region in question is greater than or equal to90%. In the mixed region including solid-section fibers andhollow-section fibers in a mixed state, located between thesolid-section fiber main region and the hollow-section fiber mainregion, the percentage of the number of solid-section fibers in thetotal number of fibers included in this region is less than that in thesolid-section fiber main region, and the percentage of the number ofhollow-section fibers in the total number of fibers included in thisregion is less than that in the hollow-section fiber main region. Thatis, the mixed region means a region where the number of solid-sectionfibers and the number of hollow-section fibers are each less than 90% ofthe total number of fibers included in this region.

The percentages of the numbers of fibers in a given region are measuredin the following manner. First, a specimen is cut into a size of 3 cmwide×3 cm long×specimen thickness to obtain 10 samples, and the weightof each sample is measured with an electronic balance. Thereafter,fibers constituting the specimen are extracted one by one from the samefront face of the samples so that the sample thickness decreases asuniformly as possible. The work of extracting fibers one by one iscontinued until the sample weight first becomes less than or equal to90% of the weight of the first-prepared sample. The cross sections ofthe extracted fibers are checked visually or with an optical microscope,etc., to separate solid-section fibers from hollow-section fibers andcount the number of solid-section fibers and the number ofhollow-section fibers. The numbers of solid-section fibers and thenumbers of hollow-section fibers of 10 samples are summed, to determinethe value as the total number of fibers included in the region. From thenumber of solid-section fibers and the number of hollow-section fiberswith respect to the total number of fibers included in the region, thepercentages of the number of solid-section fibers and the number ofhollow-section fibers are respectively calculated, to determine whetherthe region is a solid-section fiber main region, a hollow-section fibermain region, or a mixed region.

The work of extracting fibers from each sample is then restarted,continuing the work of extracting fibers one by one until the sampleweight first becomes less than or equal to 80% of the weight of thefirst-prepared sample, and, as in the manner described above, from thenumber of solid-section fibers and the number of hollow-section fiberswith respect to the total number of fibers included in the region, thepercentages of the number of solid-section fibers and the number ofhollow-section fibers are respectively calculated, to determine whetherthe region is a solid-section fiber main region, a hollow-section fibermain region, or a mixed region.

Thereafter, the work of extracting fibers from each sample is repeatedevery about 10% of sample weight, i.e., until the sample weight firstbecomes less than or equal to 70% of the weight of the first-preparedsample, until the sample weight first becomes less than or equal to 60%of the weight of the first-prepared sample, until the sample weightfirst becomes less than or equal to 50% of the weight of thefirst-prepared sample, until the sample weight first becomes less thanor equal to 40% of the weight of the first-prepared sample, until thesample weight first becomes less than or equal to 30% of the weight ofthe first-prepared sample, until the sample weight first becomes lessthan or equal to 20% of the weight of the first-prepared sample, untilthe sample weight first becomes less than or equal to 10% of the weightof the first-prepared sample, and further until the sample weightbecomes 0%. As in the manner described above, from the number ofsolid-section fibers and the number of hollow-section fibers withrespect to the total number of fibers included in each of 10 regionsdivided in the thickness direction from the front face, the percentagesof the number of solid-section fibers and the number of hollow-sectionfibers are respectively calculated, to determine whether each region isa solid-section fiber main region, a hollow-section fiber main region,or a mixed region.

Another feature of the present invention is that the difference incompression durability at pressurization from the side of thesolid-section fiber main region of the net-like structure and atpressurization from the side of the hollow-section fiber main regionthereof is small. Specifically, the difference between the solid-sectionfiber main region-side residual strain after 750 N constant loadrepeated compression at pressurization from the solid-section fiber mainregion side and the hollow-section fiber main region-side residualstrain after 750 N constant load repeated compression at pressurizationfrom the hollow-section fiber main region side is less than or equal to10 points, preferably less than or equal to 9 points, more preferablyless than or equal to 8 points, even more preferably less than or equalto 6 points. If the difference between the solid-section fiber mainregion-side residual strain and the hollow-section fiber mainregion-side residual strain after 750 N constant load repeatedcompression exceeds 10 points, the difference in compression durabilitywill be too large between the solid-section fiber main region side andthe hollow-section fiber main region side. This is not preferablebecause the wear-and-tear state of the net-like structure will vary withthe use direction when the net-like structure of the present inventionis used reversibly. The lower limit of the difference between thesolid-section fiber main region-side residual strain and thehollow-section fiber main region-side residual strain after 750 Nconstant load repeated compression is 0 point where there is nodifference in compression durability between the solid-section fibermain region side and the hollow-section fiber main region side. As usedherein, the wording “difference” refers to a value obtained bysubtracting the smaller one of two values from the larger one. Thewording “point” is a unit representing a difference between two valuesin “%.” For example, it is a unit representing the difference betweenthe solid-section fiber main region-side residual strain and thehollow-section fiber main region-side residual strain.

Both the solid-section fiber main region-side residual strain and thehollow-section fiber main region-side residual strain of the net-likestructure of the present invention are less than or equal to 20%,preferably less than or equal to 15%, more preferably less than or equalto 13%, even more preferably less than or equal to 11%. At least eitherthe solid-section fiber main region-side residual strain or thehollow-section fiber main region-side residual strain being a high valuemeans that the compression durability is poor.

In the residual strain after 750 N constant load repeated compression,in order to reduce the difference between the solid-section fiber mainregion-side residual strain and the hollow-section fiber mainregion-side residual strain, it is important to allow the presence of amixed region including solid-section fibers and hollow-section fibers ina mixed state at a position between the solid-section fiber main regionand the hollow-section fiber main region, so that these regions areintegrated, not separated from one another, thereby forming thethickness of the entire net-like structure.

It is possible to impart cushioning performance different between bothfaces even with a 2-stack layered net-like structure where a net-likestructure mainly including solid-section fibers and a net-like structuremainly including hollow-section fibers are merely stacked on each otherwithout the presence of a mixed region including solid-section fibersand hollow-section fibers in a mixed state, and they can be easilyseparated and are not integrated. However, in such a stack layerednet-like structure, when pressurizing compression is performed from theface of the net-like structure low in compression hardness, only thenet-like structure low in compression hardness is first deformed bycompression, whereby only the net-like structure low in compressionhardness becomes deflected independently from the net-like structurehigh in compression hardness. It is only at the stage when the net-likestructure low in compression hardness alone can no more stand thecompression load that the compression stress propagates to the net-likestructure high in compression hardness, at which deformation anddeflection of the net-like structure high in compression hardness start.Therefore, when pressurizing compression is repeated, fatigue builds upfirst in the net-like structure low in compression hardness, wherebyreduction in thickness and reduction in compression hardness proceedfaster than the net-like structure high in compression hardness. Thatis, while such a layered net-like structure can exert cushioningperformance different between both faces, the difference in compressiondurability at pressurization from both faces is great.

It is also possible to impart cushioning performance different betweenboth faces even with a 2-bond layered net-like structure where anet-like structure mainly including solid-section fibers and a net-likestructure mainly including hollow-section fibers are bonded together byadhesion without the presence of a mixed region including solid-sectionfibers and hollow-section fibers in a mixed state. However, in such abond layered net-like structure, while, at the initial stage of repeatedcompression, both net-like structures are deformed and deflected underpressurizing compression load in an integrated manner, stress isconcentrated on the bonding plane as compression is repeated, causingreduction in adhesion force and coming off Therefore, in this 2-bondlayered net-like structure, also, the difference in compressiondurability at pressurization from both faces is great.

It is also possible to impart cushioning performance different betweenboth faces even with a net-like structure where a solid-section fibermain region mainly including solid-section fibers and a hollow-sectionfiber main region mainly including hollow-section fibers are integratedby fusion without the presence of a mixed region including solid-sectionfibers and hollow-section fibers in a mixed state. Such a net-likestructure can be obtained by a method of stacking by fusion a net-likestructure mainly including solid-section fibers by dischargingsolid-section fibers onto a net-like structure mainly includinghollow-section fibers. However, in the net-like structure obtained bythis method, since solid-section fibers are fused after hollow-sectionfibers have been solidified, the fusion bonding force on the boundarybetween the hollow-section fiber layer and the solid-section fiber layeris low, whereby stress is concentrated on the boundary as compressionload is repeatedly applied, causing interfacial peeling, resulting indeterioration in durability.

The net-like structure of the present invention has a mixed regionincluding solid-section fibers and hollow-section fibers in a mixedstate located between the solid-section fiber main region and thehollow-section fiber main region, and these regions are integrated, notseparated from one another, thereby forming the thickness of the entirenet-like structure. With this structure, even when pressurizingcompression is performed from the side low in compression hardness,stress propagates to the side high in compression hardness through themixed region from the initial stage of compression. Stress is thereforedispersed effectively in the thickness direction, and the entirenet-like structure deforms and deflects against pressurizing compressionload. This has made it possible to reduce the difference between therepeated compression durability at pressurization from the side low incompression hardness and the repeated compression durability atpressurization from the side high in compression hardness.

The net-like structure of the present invention is obtained by addingnew technology to the known method described in Japanese PatentLaying-Open No. 2014-194099, etc. For example, a thermoplastic elastomerthat is either a polyester-based thermoplastic elastomer or apolyolefin-based thermoplastic elastomer is distributed to nozzleorifices from a multi-row nozzle that has a plurality of orifices havinga plurality of different orifice hole sizes to be described later, anddischarged downward from the nozzle at a spinning temperature (meltingtemperature) higher than the melting point of the thermoplasticelastomer by a temperature greater than or equal to 20° C. and less than120° C. Continuous linear bodies are brought into contact with oneanother in a molten state and fused together to form a three-dimensionalstructure, which is simultaneously sandwiched by take-up conveyer nets,cooled with cooling water in a cooling bath, then drawn out, and drainedor dried, to obtain a net-like structure with both faces or one facesmoothed. When only one face is to be smoothed, the elastomer may bedischarged onto an inclined take-up net, and continuous linear bodiesmay be brought into contact with one another in a molten state and fusedtogether to form a three-dimensional structure, which may besimultaneously cooled while the form of only the take-up net face isrelaxed. The obtained net-like structure can also be subjected toannealing treatment. Note that drying treatment of the net-likestructure may be regarded as annealing treatment.

The obtained net-like structure can be subjected to heat treatment(annealing treatment). The heat treatment is preferably performed at atemperature less than or equal to the melting point of the thermoplasticelastomer: preferably at a temperature less than the melting point bygreater than or equal to 5° C., more preferably at a temperature lessthan the melting point by greater than or equal to 10° C. The heattreatment temperature is preferably greater than or equal to 90° C.,more preferably greater than or equal to 95° C., even more preferablygreater than or equal to 100° C. for the polyester-based thermoplasticelastomer, and preferably greater than or equal to 70° C., morepreferably greater than or equal to 80° C., even more preferably greaterthan or equal to 90° C. for the polyolefin-based thermoplasticelastomer. The heat treatment time is preferably greater than or equalto 1 minute, more preferably greater than or equal to 10 minutes, evenmore preferably greater than or equal to 20 minutes, especiallypreferably greater than or equal to 30 minutes. While a longer heattreatment time is preferable, a heat treatment time exceeding a giventime no more increases the effect of the heat treatment but converselycauses degradation of resin. It is therefore preferred to perform theheat treatment within one hour.

The continuous linear bodies constituting the net-like structure of thepresent invention preferably have an endothermic peak at a temperaturefrom room temperature (20° C.) to less than or equal to the meltingpoint in the melting curve when measured with a differential scanningtype calorimeter. Two or more such endothermic peaks may be present, ora shoulder-like endothermic peak may appear depending on the proximityto the melting point and the base line shape. The heat and wet-heatresistance improves for one having an endothermic peak, compared withone having no endothermic peak. As usages of the heat and wear-and-tearresistance improving effect according to the present invention,applications in environments where the temperature may becomecomparatively high and compression is comparatively repeated, such ascushions for vehicles where a heater is used and flooring mats forheated floors, are useful because durability is good.

As a means for obtaining the net-like structure of the presentinvention, it is preferred to optimize the nozzle shape and dimensionsand the arrangement of nozzle holes. As for the nozzle shape, theorifice size for forming thin fibers is preferably less than or equal to1.5 mm, and the orifice size for forming thick fibers is preferablygreater than or equal to 2 mm. The nozzle orifice shape for formingthick fibers preferably has a hollow forming property. Examples of suchnozzles include a C-type nozzle and a triple bridge shaped nozzle. Fromthe standpoint of durability, a triple bridge shaped nozzle ispreferable. The inter-hole pitch is preferably greater than or equal to4 mm and less than or equal to 12 mm, more preferably greater than orequal to 5 mm and less than or equal to 11 mm, for both orifices forforming thin fibers and orifices for forming thick fibers. Examples ofthe arrangement of nozzle holes include lattice arrangement,circumferential arrangement, and zigzag arrangement. From the standpointof the quality of the net-like structure, lattice arrangement or zigzagarrangement is preferable. The inter-hole pitch as used herein refers tothe distance between the centers of nozzle holes, and has an inter-holepitch in the width direction of the net-like structure (hereinafterreferred to as a “width-direction inter-hole pitch”) and an inter-holepitch in the thickness direction of the net-like structure (hereinafterreferred to as a “thickness-direction inter-hole pitch”). The preferableinter-hole pitch described above is an inter-hole pitch suitable forboth the width-direction inter-hole pitch and the thickness-directioninter-hole pitch.

A nozzle for obtaining the net-like structure of the present inventionis constituted of three groups (a group, ab mixed group, and b group),that is,

a group: an orifice hole group where orifice holes for solid-sectionfibers are arranged in a plurality of rows in the thickness direction,

ab mixed group: an orifice hole group where orifice holes forsolid-section fibers and orifice holes for hollow-section fibers arearranged in a mixed state in a plurality of rows in the thicknessdirection, and

b group: an orifice hole group where orifice holes for hollow-sectionfibers are arranged in a plurality of rows in the thickness direction.

As another nozzle, there is a nozzle constituted of two groups (α groupand β group), that is,

α group: an orifice hole group where orifice holes for solid-sectionfibers are arranged in a plurality of rows in the thickness direction,and

β group: an orifice hole group where orifice holes for hollow-sectionfibers are arranged in a plurality of rows in the thickness direction,

and the difference between the width-direction inter-hole pitch oforifices for solid-section fibers and the width-direction inter-holepitch of orifices for hollow-section fibers is small. From thestandpoint that the structure of the nozzle can be simplified, thenozzle constituted of α group and β group is more preferable.

Although the nozzle has only two orifice hole groups, fibers spun fromnear the boundary between α group and β group form a mixed region havingsolid-section fibers and hollow-section fibers in a mixed state.Therefore, the net-like structure of the present invention having threeregions in the thickness direction can be obtained.

In order to obtain the net-like structure of the present invention wherethe difference in compression durability is small from whichever facepressure is applied, it is necessary to reduce the difference betweenthe width-direction inter-hole pitch of orifices for solid-sectionfibers and the width-direction inter-hole pitch of orifices forhollow-section fibers. The reason why the difference in durability issmall when the difference in width-direction inter-hole pitch is smallhas not been clarified completely, but is presumed as follows.

Being small in the difference in the width-direction inter-hole pitch oforifices in the mixed region including solid-section fibers andhollow-section fibers in a mixed state means that the numbers ofconstituent solid-section fibers and hollow-section fibers in the mixedregion are close to each other. When the numbers of constituentsolid-section fibers and hollow-section fibers are close to each other,it is indicative that solid-section fibers and hollow-section fibersconstitute a plurality of contact points in a roughly one-to-onerelationship. Therefore, it is considered that stress easily propagatesfrom whichever face pressure is applied, whereby the difference incompression durability is small from whichever face pressure is applied.

On the contrary, the case is considered where a net-like structure isformed using a nozzle large in the difference in the width-directioninter-hole pitch of orifices. When the number of constituentsolid-section fibers is large compared with the number of constituenthollow-section fibers in the mixed region including solid-section fibersand hollow-section fibers in a mixed state, some of the solid-sectionfibers hardly have contact points with hollow-section fibers in themixed region. Therefore, it is considered that, at pressurization fromthe side of hollow-section fibers, there are solid-section fibers towhich stress hardly propagate from hollow-section fibers, and suchsolid-section fibers receive stress via other solid-section fibers towhich stress has propagated from hollow-section fibers. Conversely, itis considered that, at pressurization from the side of solid-sectionfibers, there are solid-section fibers that cannot propagate stress tohollow-section fibers, and such solid-section fibers propagate stress tohollow-section fibers via other solid-section fibers that can propagatestress to hollow-section fibers.

In other words, it is considered that, when a net-like structure isformed using a nozzle large in the difference in the width-directioninter-hole pitch of orifices, the propagation of stress is dispersed inthe thickness direction and directions orthogonal to the thicknessdirection in the mixed region including solid-section fibers andhollow-section fibers in a mixed state, reducing the stress propagationefficiency, and thus the difference in compression durability is largebetween the case of pressurization from the side of solid-section fibersand the case of pressurization from the side of hollow-section fibers.

The difference between the width-direction inter-hole pitch of orificesfor solid-section fibers and the width-direction inter-hole pitch oforifices for hollow-section fibers is preferably less than or equal to 2mm, more preferably less than or equal to 1 mm, even more preferably 0mm, in which, namely, the width-direction inter-hole pitches are thesame.

The fiber size (average fiber size: this also applies to descriptionbelow) of the continuous linear bodies constituting the net-likestructure of the present invention is greater than or equal to 0.1 mmand less than or equal to 3.0 mm, preferably greater than or equal to0.2 mm and less than or equal to 2.5 mm, more preferably greater than orequal to 0.3 mm and less than or equal to 2.0 mm. If the fiber size isless than 0.1 mm, the continuous linear bodies will be so fine that,while compactness and soft touch will be good, it will be difficult tosecure the hardness required for the net-like structure. If the fibersize exceeds 3.0 mm, while the hardness of the net-like structure may besufficiently secured, the net-like structure may be coarse, degradingother cushioning performance. From this standpoint, it is necessary toset the plurality of fiber sizes within a proper range.

In the continuous linear bodies constituting the net-like structure ofthe present invention, since hollow-section fibers are high in secondmoment of area than solid-section fibers given that the fineness is thesame, resistance to compression is higher when hollow-section fibers areused. Therefore, in order to obtain cushioning performance differentmore significantly between both faces, the fiber size of hollow-sectionfibers is preferably large compared with the fiber size of solid-sectionfibers.

The difference in fiber size (difference in average fiber size; thisalso applies to description below) between hollow-section fibers andsolid-section fibers of the continuous linear bodies constituting thenet-like structure of the present invention is preferably greater thanor equal to 0.07 mm, more preferably greater than or equal to 0.10 mm,even more preferably greater than or equal to 0.12 mm, especiallypreferably greater than or equal to 0.15 mm, more especially preferablygreater than or equal to 0.20 mm, most preferably greater than or equalto 0.25 mm. The upper limit of the difference in fiber size ispreferably less than or equal to 2.5 mm according to the presentinvention. If the difference in fiber size is less than 0.07 mm, thedifference in cushioning performance between both faces will be small.If the difference in fiber size is excessively large, there will be anexcessive feeling of strangeness. It is therefore necessary to set thedifference in fiber size within a proper range.

The total weight ratio of solid-section fibers constituting the net-likestructure of the present invention is preferably greater than or equalto 10% and less than or equal to 90% with respect to all fibersconstituting the net-like structure. In order to impart goodreversibility to the net-like structure of the present invention, theratio is more preferably greater than or equal to 20% and less than orequal to 80%, even more preferably greater than or equal to 30% and lessthan or equal to 70%. If the ratio is less than 10% or exceeds 90%, thedifference in cushioning performance will be small.

The continuous linear bodies constituting the net-like structure of thepresent invention may be combined with another thermoplastic resin toform complex linear bodies within the bounds of not impairing the objectof the present invention. When the linear bodies themselves arecomplexed, examples of the complex form include complex linear bodies ofsheath core type, side-by-side type, and eccentric sheath core type.

The cross-sectional shape of the continuous linear bodies constitutingthe net-like structure of the present invention is preferably roughlycircular for both solid-section fibers and hollow-section fibers. Insome cases, however, compression resistance and touch can be imparted byproviding an abnormal cross section.

The net-like structure of the present invention can be subjected totreatment processing such as addition of chemicals to impart functionssuch as antibacterial deodorization, deodorization, mold prevention,coloring, fragrance, flame resisting, and absorption and desorption ofmoisture, at any given stage from a resin manufacturing process toprocessing into a molded body and commercialization, within the boundsof not deteriorating the performance.

The net-like structure of the present invention includes structuresformed into any shape. For example, included are net-like structureshaving shapes of a plate, a triangle pole, a polyhedron, a cylinder, anda sphere and a shape including many of these shapes. Such structures canbe formed by a known method such as cutting, hot pressing, andprocessing of nonwoven fabric.

The net-like structure of the present invention also includes a net-likestructure having the net-like structure of the present invention as apart thereof.

The apparent density of the net-like structure of the present inventionis preferably greater than or equal to 0.005 g/cm³ and less than orequal to 0.20 g/cm³, more preferably greater than or equal to 0.01 g/cm³and less than or equal to 0.18 g/cm³, even more preferably greater thanor equal to 0.02 g/cm³ and less than or equal to 0.15 g/cm³. If theapparent density is less than 0.005 g/cm³, the required hardness cannotbe secured when the net-like structure is used as a cushion material. Ifthe apparent density exceeds 0.20 g/cm³, the net-like structure may betoo hard to be suitable for a cushion material.

The thickness of the net-like structure of the present invention ispreferably greater than or equal to 5 mm, more preferably greater thanor equal to 10 mm. If the thickness is less than 5 mm, the net-likestructure will be so thin for use as a cushion material that a bottomtouch feeling may occur. The upper limit of the thickness is preferablyless than or equal to 300 mm, more preferably less than or equal to 200mm, even more preferably less than or equal to 120 mm from thestandpoint of manufacturing equipment.

In the net-like structure of the present invention, for the net-likestructure having a three-dimensional random loop bonded structureconstituted of a polyester-based thermoplastic elastomer, both thehardness at 25% compression at pressurization from the solid-sectionfiber main region side and the hardness at 25% compression atpressurization from the hollow-section fiber main region side arepreferably greater than or equal to 10 N/ϕ100 mm, more preferablygreater than or equal to 20 N/ϕ100 mm. If the 25% compression hardnessis less than 10 N/ϕ100 mm, the hardness as a cushion material will beinsufficient, and a bottom touch feeling may occur. The upper limit ofthe 25% compression hardness is not particularly specified, butpreferably less than or equal to 1.5 kN/ϕ100 mm.

For the net-like structure having a three-dimensional random loop bondedstructure constituted of a polyolefin-based thermoplastic elastomer,both the 25% compression hardness at pressurization from thesolid-section fiber main region side and the 25% compression hardness atpressurization from the hollow-section fiber main region side arepreferably greater than or equal to 2 N/ϕ100 mm, more preferably greaterthan or equal to 5 N/ϕ100 mm. If the 25% compression hardness is lessthan 2 N/ϕ100 mm, the hardness as a cushion material will beinsufficient, and a bottom touch feeling may occur. The upper limit ofthe 25% compression hardness is not particularly specified, butpreferably less than or equal to 1.5 kN/ϕ100 mm.

In the net-like structure of the present invention, whether it isconstituted of a polyester-based thermoplastic elastomer or apolyolefin-based thermoplastic elastomer, the ratio between the 25%compression hardness at pressurization from the solid-section fiber mainregion side and the 25% compression hardness at pressurization from thehollow-section fiber main region side is preferably greater than orequal to 1.03, more preferably greater than or equal to 1.05, even morepreferably greater than or equal to 1.07, especially preferably greaterthan or equal to 1.10, most preferably greater than or equal to 1.20. Ifthe ratio of the 25% compression hardness is less than 1.03, thedifference in cushioning performance between both faces will be small.As used herein, the wording “ratio” refers to a ratio of the larger oneof two values to the smaller one, which is equal to a value obtained bydividing the larger value by the smaller value.

In the net-like structure of the present invention, for the net-likestructure having a three-dimensional random loop bonded structureconstituted of a polyester-based thermoplastic elastomer, both the 40%compression hardness at pressurization from the solid-section fiber mainregion side and the 40% compression hardness at pressurization from thehollow-section fiber main region side are preferably greater than orequal to 20 N/ϕ100 mm, more preferably greater than or equal to 30N/ϕ100 mm, even more preferably greater than or equal to 40 N/ϕ100 mm.If the 40% compression hardness is less than 20 N/ϕ100 mm, the hardnessas a cushion material will be insufficient, and a bottom touch feelingmay occur. The upper limit of the 40% compression hardness is notparticularly specified, but preferably less than or equal to 5 kN/ϕ100mm.

For the net-like structure having a three-dimensional random loop bondedstructure constituted of a polyolefin-based thermoplastic elastomer,both the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side arepreferably greater than or equal to 5 N/ϕ100 mm, more preferably greaterthan or equal to 10 N/ϕ100 mm, even more preferably greater than orequal to 15 N/ϕ100 mm. If the 40% compression hardness is less than 5N/ϕ100 mm, the hardness as a cushion material will be insufficient, anda bottom touch feeling may occur. The upper limit of the 40% compressionhardness is not particularly specified, but preferably less than orequal to 5 kN/ϕ100 mm.

In the net-like structure of the present invention, whether it isconstituted of a polyester-based thermoplastic elastomer or apolyolefin-based thermoplastic elastomer, the ratio between the 40%compression hardness at pressurization from the solid-section fiber mainregion side and the 40% compression hardness at pressurization from thehollow-section fiber main region side is preferably greater than orequal to 1.05, more preferably greater than or equal to 1.07, even morepreferably greater than or equal to 1.10, especially preferably greaterthan or equal to 1.15, most preferably greater than or equal to 1.20. Ifthe ratio of the 40% compression hardness is less than 1.05, thedifference in cushioning performance between both faces will be small.

In the net-like structure of the present invention, whether the net-likestructure is constituted of a polyester-based thermoplastic elastomer ora polyolefin-based thermoplastic elastomer, both the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side arepreferably greater than or equal to 2.5 and less than or equal to 10.0,more preferably greater than or equal to 2.6 and less than or equal to9.0, even more preferably greater than or equal to 2.7 and less than orequal to 8.0. If the compression deflection coefficient is less than2.5, the difference in cushioning performance with a change incompression ratio will be small, and this may worsen comfort to sleep onand comfort to sit on. If it exceeds 10.0, the difference in cushioningperformance will be excessively large with a change in compressionratio, and this may cause a bottom touch feeling and a feeling ofstrangeness.

In the net-like structure of the present invention, whether the net-likestructure is constituted of a polyester-based thermoplastic elastomer ora polyolefin-based thermoplastic elastomer, the difference between thecompression deflection coefficient at pressurization from thesolid-section fiber main region side and the compression deflectioncoefficient at pressurization from the hollow-section fiber main regionside is preferably less than or equal to 5. If the difference betweenthe compression deflection coefficients exceeds 5, a bottom touchfeeling and a feeling of strangeness may occur at the use of the facewhere the compression deflection coefficient is higher. The lower limitof the difference between the compression deflection coefficients is notparticularly specified, but, according to the present invention,preferably 0 where there is no difference at all.

In the net-like structure of the present invention, for the net-likestructure having a three-dimensional random loop bonded structureconstituted of a polyester-based thermoplastic elastomer, both thehysteresis losses at pressurization from the solid-section fiber mainregion side and the hollow-section fiber main region side are preferablyless than or equal to 30%, more preferably less than or equal to 29%,even more preferably less than or equal to 28%, especially preferablyless than or equal to 26%. If the hysteresis loss exceeds 30%,highly-resilient comfort to sleep on and comfort to sit on, provided bythe net-like structure of the present invention, will no more beretained. The lower limit of the hysteresis loss is not particularlyspecified, but preferably greater than or equal to 1%.

For the net-like structure having a three-dimensional random loop bondedstructure constituted of a polyolefin-based thermoplastic elastomer,both the hysteresis losses at pressurization from the solid-sectionfiber main region side and the hollow-section fiber main region side arepreferably less than or equal to 60%, more preferably less than or equalto 55%, even more preferably less than or equal to 50%, especiallypreferably less than or equal to 45%. If the hysteresis loss exceeds60%, highly-resilient comfort to sleep on and comfort to sit on,provided by the net-like structure of the present invention, will nomore be retained. The lower limit of the hysteresis loss is notparticularly specified, but preferably greater than or equal to 1%.

In the net-like structure of the present invention, whether the net-likestructure is constituted of a polyester-based thermoplastic elastomer ora polyolefin-based thermoplastic elastomer, the hysteresis loss on theside of lower hardness at compression tends to be higher than thehysteresis loss on the side of higher hardness at compression, incomparison between the hysteresis loss at pressurization from thesolid-section fiber main region side and the hysteresis loss atpressurization from the hollow-section fiber main region side.

According to the present invention, the residual strain after 750 Nconstant load repeated compression, the 25%, 40%, and 65% compressionhardness, and the hysteresis losses at pressurization from thesolid-section fiber main region side and the hollow-section fiber mainregion side can be measured using a universal tester such as Instronuniversal tester manufactured by Instron Japan Co., Ltd., precisionuniversal tester Autograph AG-X plus manufactured by SHIMAZDUCORPORATION, and TENSILON universal tester manufactured by Orientec Co.,Ltd.

In the net-like structure of the present invention, the differencebetween the hysteresis loss at pressurization from the solid-sectionfiber main region side and the hysteresis loss at pressurization fromthe hollow-section fiber main region side is preferably less than orequal to 5 points. If the difference between the hysteresis lossesexceeds 5 points, highly-resilient comfort to sleep on and comfort tosit on, provided by the net-like structure, will no more be retained.The lower limit of the hysteresis loss is not particularly specified,but, according to the present invention, preferably greater than orequal to 0 point where there is no difference at all.

The thus-obtained net-like structure of the present invention isprovided with cushioning performance different between both faces. Inmanufacturing conventional mats provided with cushioning performancedifferent between both faces, another net-like structure different indesign, hard cotton, urethane, or the like was stacked on the net-likestructure inside a fabric case. Although these are excellent incushioning performance, there have been problems as follows: thecompression durability is different between the case of use from oneface and the case of use from the other face; since the manufacturingcost is high, the resultant product is comparatively expensive, andsince sorted recovery is necessary, recycling is cumbersome. Thenet-like structure of the present invention that is small in differencein compression durability between both faces and provided withcushioning performance different between both faces can solve the aboveproblems.

The cushion material according to the present invention includes theabove net-like structure inside the cushion and can be used reversibly.According to the present invention, being usable reversibly means that acushion material can be used from either side, the solid-section fibermain region side or the hollow-section fiber main region side, of thenet-like structure included in the cushion material. Therefore, a usemode of using a cushion material only from one side, the solid-sectionfiber main region side or the hollow-section fiber main region side,also corresponds with the use according to the present invention.

EXAMPLES

While the present invention will be described hereinafter concretelywith reference to examples, the present invention is not limited tothese examples. Measurement and evaluation of property values inexamples were performed in the following manners. Note that, while thesizes of specimens described below were considered standard, a possiblespecimen size was used for measurement when the quantity of specimenswas insufficient.

(1) Fiber Size (Mm)

A specimen was cut into a size of 10 cm wide×10 cm long×specimenthickness, and linear bodies of 10 solid-section fibers and 10hollow-section fibers were collected by a length of about 5 mm randomlyin the thickness direction from the cut cross section. The collectedlinear bodies were observed with an optical microscope with anappropriate magnification, focusing on a fiber size measurement point,to measure the fiber size as viewed from the fiber side face. As theaverage fiber size, the average in each of regions different in fibersize was calculated (unit: mm) (average value of n=10 each). That is,the fiber sizes of the solid-section fibers and the hollow-sectionfibers respectively mean the average fiber sizes of the solid-sectionfibers and the hollow-section fibers. As for the measurement of thefiber size in Comparative Examples I-2 and II-1, 10 fibers werecollected by a length of about 5 mm randomly in the thickness directionfrom the cut cross section, and were observed with an optical microscopewith an appropriate magnification, focusing on a fiber size measurementpoint, to measure the fiber size as viewed from the fiber side face.Since the surface of the net-like structure is made flat to obtainsmoothness, the fiber cross section may be deformed. For this reason, itwas decided not to collect a specimen in a region within 2 mm from thesurface of the net-like structure.

(2) Difference in Fiber Size (Mm)

The difference between the averages of the fiber sizes of thesolid-section fibers and the hollow-section fibers measured in (1) abovewas determined, to calculate the difference in fiber size according tothe formula below.

(Difference in fiber size)=|(Average of fiber sizes of hollow-sectionfibers)−(Average of fiber sizes of solid-section fibers)|(unit: mm)

That is, the difference in fiber size between solid-section fibers andhollow-section fibers means the difference between the average fibersize of solid-section fibers and the average fiber size ofhollow-section fibers. In Comparative Example 1-2 and II-1, thedifference in fiber size was calculated according to the formula below.

(Difference in fiber size)=(Average of fiber sizes of thickfibers)−(Average of fiber sizes of thin fibers) (unit: mm)

The above meaning also applies to the difference in fiber size betweenthick fibers and thin fibers.

(3) Total Weight Ratio of Solid-Section Fibers (%)

A specimen was cut into a size of 5 cm wide×5 cm long×specimenthickness. Fibers constituting the specimen were checked visually orwith an optical microscope, etc. and sorted into solid-section fibersand hollow-section fibers. Thereafter, the total weight of only thesolid-section fibers and the total weight of only the hollow-sectionfibers were measured. The total weight ratio of the solid-section fiberswas calculated according to the formula below.

(Total weight ratio of solid-section fibers)=(Total weight ofsolid-section fibers)/(Total weight of solid-section fibers+Total weightof hollow-section fibers)×100 (unit: %)

(4) Hollowness (%)

A specimen was cut into a size of 5 cm wide×5 cm long×specimenthickness, and 10 linear bodies of hollow-section fibers were collectedrandomly in the thickness direction from a cut cross section in a regionof the specimen except for the ranges within 10% from both faces of thespecimen in the thickness direction. The collected linear bodies werecut in a slicing direction, and placed on cover glass in a standingstate along the fiber axis, to obtain a fiber cross-sectional picture inthe slicing direction with an optical microscope. From thecross-sectional picture, a hollow part area (a) and the total area (b)of the fiber including the hollow part were determined, to calculate thehollowness according to the formula below.

(Hollowness)=(a)/(b)×100 (unit: %, average of n=10)

(5) Thickness and Apparent Density (Mm and g/Cm³)

A specimen was cut into a size of 10 cm wide×10 cm long×specimenthickness to obtain 4 samples, and the samples were left standing withno load for 24 hours. Thereafter, the height at one point of each samplewas measured, with the side of solid-section fibers facing up, using acircular probe having an area of 15 cm² with a thickness gauge ModelFD-80N manufactured by Kobunshi Keiki Co., Ltd., to determine theaverage of the 4 samples as the thickness. The weight was also measuredby placing the specimen on an electronic balance, to determine theaverage of the weights of the 4 samples as the weight. The apparentdensity was calculated from the average specimen weight and the averagespecimen thickness according to the formula below.

(Apparent density)=(Weight)/(Thickness×10×10) (unit: g/cm³)

(6) Melting Point (Tm) (° C.)

An endothermic peak (melting peak) temperature was determined from anendothermic/exothermic curve measured at a temperature rise rate of 20°C./min using a differential scanning calorimeter Q200 manufactured by TAInstruments.

(7) Residual Strain after 750 N Constant Load Repeated Compression (%)

A specimen was cut into a size of 40 cm wide×40 cm long×specimenthickness, and the cut sample was left standing with no load for 24hours under an environment of 23° C.±2° C., and then measured using auniversal tester (Instron universal tester manufactured by Instron JapanCo., Ltd.) that was under an environment of 23° C.±2° C. The sample wasplaced in the tester so as to be in the center with respect to apressure plate having a diameter of 200 mm and a thickness of 3 mm, andthe thickness at the time when a load of 5 N was detected by theuniversal tester was measured as an initial hardness meter thickness(c). Immediately after this measurement, the thickness-measured samplewas subjected to 750 N constant load repeated compression using ASKERSTM-536 in conformity with JIS K6400-4 (2004) A Method (Constant LoadMethod). As the pressurizer, used was one having a shape of a circlehaving a diameter of 250±1 mm and a thickness of 3 mm, with a radius ofcurvature of 25±1 mm at an edge portion of the bottom face and having aflat lower face. The load was 750 N±20 N, the compression frequency was70±5 times per minute, the number of times of repeated compression was80,000, the percentage of the time during which the sample waspressurized at the maximum 750±20 N was less than or equal to 25% of thetime required for repeated compression. After termination of therepeated compression, the test piece was left standing in anon-pressurized state for 10±0.5 minutes. Using a universal tester(Instron universal tester manufactured by Instron Japan Co., Ltd.), thesample was placed in the tester so as to be in the center with respectto a pressure plate having a diameter of 200 mm and a thickness of 3 mm,and the thickness at the time when a load of 5 N was detected by theuniversal tester was measured as a hardness meter thickness (d) afterrepeated compression. The residual strain after 750 N constant loadrepeated compression was calculated using the initial hardness meterthickness (c) and the hardness meter thickness (d) after repeatedcompression according to the formula below.

(Residual strain after 750 N constant load repeatedcompression)={(c)−(d)}/(c)×100 (unit: %, average of n=3)

The above measurement was performed for each of the case ofpressurization from the solid-section fiber main region side and thecase of pressurization from the hollow-section fiber main region side.Note that separate samples were prepared and used for measurement of theresidual strain in the case of pressurization from the solid-sectionfiber main region side, which is hereinafter referred to as thesolid-section fiber main region-side residual strain, and the residualstrain in the case of pressurization from the hollow-section fiber mainregion side, which is hereinafter referred to as the hollow-sectionfiber main region-side residual strain.

(8) Difference Between Solid-Section Fiber Main Region-Side ResidualStrain and Hollow-Section Fiber Main Region-Side Residual Strain (Point)

Using the solid-section fiber main region-side residual strain and thehollow-section fiber main region-side residual strain calculated in (7)above, the difference was calculated according to the formula below.

(Difference between residual strain after 750 N constant load repeatedcompression at pressurization from solid-section fiber main region sideand residual strain after 750 N constant load repeated compression atpressurization from hollow-section fiber main region side)=|(Residualstrain after 750 N constant load repeated compression at pressurizationfrom solid-section fiber main region side)−(Residual strain after 750 Nconstant load repeated compression at pressurization from hollow-sectionfiber main region side)|(unit: point)

(9) 25%, 40% 65% Compression Hardness (N/ϕ100 Mm)

A specimen was cut into a size of 20 cm wide×20 cm long×specimenthickness, and was left standing with no load for 24 hours under anenvironment of 23° C.±2° C. The specimen was then placed in a universaltester (Instron universal tester manufactured by Instron Japan Co.,Ltd.) that was under an environment of 23° C.±2° C., and compression wasstarted for the center of the specimen at a speed of 1 mm/min using apressure plate having a diameter of ϕ100 mm, a thickness of 25±1 mm, anda radius of curvature of 10±1 mm at an edge portion of the bottom faceand having a flat lower face. The thickness at the time when theuniversal tester detected a load of 0.4 N was measured as a hardnessmeter thickness. Taking the position of the pressure plate at this timeas a zero point, and immediately after the measurement of the hardnessmeter thickness, the specimen was compressed to 75% of the hardnessmeter thickness at a speed of 10 mm/min, and then the pressure plate wasimmediately returned to the zero point at a speed of 10 mm/min.Subsequently, the specimen was immediately compressed to 25%, 40%, and65% of the hardness meter thickness at a speed of 10 mm/min, and theloads at these times were measured as a 25% compression hardness, a 40%compression hardness, and a 65% compression hardness, respectively(unit: N/ϕ100 mm, average of n=3). The above measurement was performedfor each of pressurization from the solid-section fiber main region sideand pressurization from the hollow-section fiber main region side. Notethat separate specimens were prepared and used for measurement of thecompression hardness on the solid-section fiber main region side andmeasurement of the compression hardness on the hollow-section fiber mainregion side.

(10) Ratio Between 25% Compression Hardness at Pressurization fromSolid-Section Fiber Main Region Side and 25% Compression Hardness atPressurization from Hollow-Section Fiber Main Region Side (−)

Using the 25% compression hardness at pressurization from each of thesolid-section fiber main region side and the hollow-section fiber mainregion side measured in (9) above, the ratio was calculated according tothe formula below depending on the following cases.

-   -   When (25% compression hardness at pressurization from        solid-section fiber main region side)≥(25% compression hardness        at pressurization from hollow-section fiber main region side)

(Ratio between 25% compression hardness at pressurization fromsolid-section fiber main region side and 25% compression hardness atpressurization from hollow-section fiber main region side)=(25%compression hardness at pressurization from solid-section fiber mainregion side)/(25% compression hardness at pressurization fromhollow-section fiber main region side)

-   -   When (25% compression hardness at pressurization from        solid-section fiber main region side)<(25% compression hardness        at pressurization from hollow-section fiber main region side)

(Ratio between 25% compression hardness at pressurization fromsolid-section fiber main region side and 25% compression hardness atpressurization from hollow-section fiber main region side)=(25%compression hardness at pressurization from hollow-section fiber mainregion side)/(25% compression hardness at pressurization fromsolid-section fiber main region side)

(11) Ratio Between 40% Compression Hardness at Pressurization fromSolid-Section Fiber Main Region Side and 40% Compression Hardness atPressurization from Hollow-Section Fiber Main Region Side (−)

Using the 40% compression hardness at pressurization from each of thesolid-section fiber main region side and the hollow-section fiber mainregion side measured in (9) above, the ratio was calculated according tothe formula below depending on the following cases.

-   -   When (40% compression hardness at pressurization from        solid-section fiber main region side)≥(40% compression hardness        at pressurization from hollow-section fiber main region side)

(Ratio between 40% compression hardness at pressurization fromsolid-section fiber main region side and 40% compression hardness atpressurization from hollow-section fiber main region side)=(40%compression hardness at pressurization from solid-section fiber mainregion side)/(40% compression hardness at pressurization fromhollow-section fiber main region side)

-   -   When (40% compression hardness at pressurization from        solid-section fiber main region side)<(40% compression hardness        at pressurization from hollow-section fiber main region side)

(Ratio between 40% compression hardness at pressurization fromsolid-section fiber main region side and 40% compression hardness atpressurization from hollow-section fiber main region side)=(40%compression hardness at pressurization from hollow-section fiber mainregion side)/(40% compression hardness at pressurization fromsolid-section fiber main region side)

(12) Compression Deflection Coefficient (−)

The compression deflection coefficient was calculated according to theformulae below:

(Compression deflection coefficient at pressurization from solid-sectionfiber main region side)=(f)/(e) (average of n=3)

(Compression deflection coefficient at pressurization fromhollow-section fiber main region side)=(h)/(g) (average of n=3)

where, as described in (9), (e) is the 25% compression hardness atpressurization from the solid-section fiber main region side, (f) is the65% compression hardness at pressurization from the solid-section fibermain region side, (g) is the 25% compression hardness at pressurizationfrom the hollow-section fiber main region side, and (h) is the 65%compression hardness at pressurization from the hollow-section fibermain region side.

(13) Difference Between Compression Deflection Coefficient atPressurization from Solid-Section Fiber Main Region Side and CompressionDeflection Coefficient at Pressurization from Hollow-Section Fiber MainRegion Side (−)

Using the compression deflection coefficients calculated in (12) above,the difference was calculated according to the formula below.

(Difference between compression deflection coefficient at pressurizationfrom solid-section fiber main region side and compression deflectioncoefficient at pressurization from hollow-section fiber mainregion)=|(Compression deflection coefficient at pressurization fromsolid-section fiber main region side)−(Compression deflectioncoefficient at pressurization from hollow-section fiber main regionside)|

(14) Hysteresis Loss (%)

A specimen was cut into a size of 20 cm wide×20 cm long×specimenthickness, and was left standing with no load for 24 hours under anenvironment of 23° C.±2° C. The specimen was then placed in a universaltester (Instron universal tester manufactured by Instron Japan Co.,Ltd.) that was under an environment of 23° C.±2° C., and compression wasstarted for the center of the specimen at a speed of 1 mm/min using apressure plate having a diameter of ϕ100 mm, a thickness of 25±1 mm, anda radius of curvature of 10±1 mm at an edge portion of the bottom faceand having a flat lower face. The thickness at the time when theuniversal tester detected a load of 0.4 N was measured as a hardnessmeter thickness. Taking the position of the pressure plate at this timeas a zero point, and immediately after the measurement of the hardnessmeter thickness, the specimen was compressed to 75% of the hardnessmeter thickness at a speed of 10 mm/min, and then the pressure plate wasimmediately returned to the zero point at a speed of 10 mm/min (firststress-strain curve). Immediately after the return to the zero point,the specimen was again compressed to 75% of the hardness meter thicknessat a speed of 10 mm/min, and then the pressure plate was immediatelyreturned to the zero point at the same speed (second stress-straincurve)

In the second stress-strain curve in FIG. 1A, using a compression energy(WC) indicated by a stress-strain curve at second compression in FIG. 1Band a compression energy (WC′) indicated by a stress-strain curve atsecond decompression in FIG. 1C, hysteresis loss was determinedaccording to the formula below.

(Hysteresis loss)=(WC−WC′)/WC×100 (unit: %)

WC=∫PdT (workload at compression from 0% to 75%)

WC′=∫PdT (workload at decompression from 75% to 0%)

As a simplified way, when stress-strain curves as shown in FIGS. 1A-1C,for example, are obtained, the hysteresis loss can be calculated by dataanalysis using a personal computer. As another way, with the area of thehatched portion being defined as WC and the area of the dotted portionas WC′, the difference between these areas can be determined from theweight of the cut-out portion (average of n=3).

The measurement of the hysteresis loss was performed for each ofpressurization from the solid-section fiber main region side andpressurization from the hollow-section fiber main region side. Note thatseparate specimens were prepared and used for measurement on thesolid-section fiber main region side and measurement on thehollow-section fiber main region side.

(15) Difference Between Hysteresis Loss at Pressurization fromSolid-Section Fiber Main Region Side and Hysteresis Loss atPressurization from Hollow-Section Fiber Main Region Side (Point)

Using the hysteresis losses calculated in (14) above, the difference wascalculated according to the formula below.

(Difference between hysteresis loss at pressurization from solid-sectionfiber main region side and hysteresis loss at pressurization fromhollow-section fiber main region side)=|(Hysteresis loss atpressurization from solid-section fiber main region side)−(Hysteresisloss at pressurization from hollow-section fiber main regionside)|(unit: point)

Example I-1

As a polyester-based thermoplastic elastomer, dimethyl terephthalate(DMT) and 1,4-butanediol (1,4-BD) were put together with a small amountof a catalyst, and, after ester exchange by a usual way, subjected topolycondensation with addition of polytetramethylene glycol (PTMG)having an average molecular weight of 1000 while temperature rise andpressure reduction were being performed, to produce a polyether-esterblock copolymerized elastomer. Thereafter, with addition of 1% of anantioxidant, the resultant elastomer was mixed and kneaded, thenpelletized, and dried in a vacuum at 50° C. for 48 hours, to obtain apolyester-based thermoplastic elastomer (A-1), which had a soft segmentcontent of 40 wt % and a melting point of 198° C.

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 67.6 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in the first toseventh rows in the thickness direction at a width-direction inter-holepitch of 6 mm and a thickness-direction inter-hole pitch of 5.2 mm andsolid forming orifices having an outer size of 1 mm were zigzag-arrangedin the eighth to fourteenth rows in the thickness direction at awidth-direction inter-hole pitch of 6 mm and a thickness-directioninter-hole pitch of 5.2 mm. The obtained polyester-based thermoplasticelastomer (A-1) was discharged downward from the nozzle at a spinningtemperature (melting temperature) of 240° C. at a single-hole dischargerate of 1.5 g/min for hollow holes and a single-hole discharge rate of0.9 g/min for solid holes. Cooling water was provided at a position 28cm below the nozzle face. Endless nets made of stainless steel eachhaving a width of 60 cm were placed in parallel at a spacing of 52 mm inopening width to form a pair of take-up conveyor nets so as to bepartially exposed over a water surface. Above the conveyer nets over thewater surface, the discharged filaments in a molten state were curled toform loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.14 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 110° C. hotair for 15 minutes, to obtain a net-like structure.

The obtained net-like structure was a net-like structure having asolid-section fiber main region mainly including solid-section fibers, ahollow-section fiber main region mainly including hollow-section fibers,and a mixed region including solid-section fibers and hollow-sectionfibers in a mixed state, located between the solid-section fiber mainregion and the hollow-section fiber main region, where these regionswere integrated, not separated from one another. The hollow-sectionfibers were formed of hollow linear bodies having a triangular rice-ballshaped hollow cross section, a hollowness of 20%, and a fiber size of0.76 mm, and the solid-section fibers were formed of solid linear bodieshaving a fiber size of 0.50 mm. The difference in fiber size was 0.26mm, the total weight ratio of the solid-section fibers was 38%, theapparent density was 0.055 g/cm³, and the thickness of flattened surfacewas 50 mm.

The hollow-section fiber main region-side residual strain was 6.7%, thesolid-section fiber main region-side residual strain was 5.7%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was1.0 point. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 45.1 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 32.1 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.40, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 75.1 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 61.3 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.23,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 4.07, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 5.99, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 1.92,the hysteresis loss at pressurization from the hollow-section fiber mainregion side was 23.7%, the hysteresis loss at pressurization from thesolid-section fiber main region side was 26.2%, and the differencebetween the hysteresis loss at pressurization from the solid-sectionfiber main region side and the hysteresis loss at pressurization fromthe hollow-section fiber main region side was 2.5 points. The propertiesof the obtained net-like structure are shown in Table 1.

As shown in Table 1, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 30% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Example I-2

A net-like structure was obtained in the same manner as in Example I-1except that cooling water was provided at a position 32 cm below thenozzle face. The obtained net-like structure was a net-like structurehaving a solid-section fiber main region mainly including solid-sectionfibers, a hollow-section fiber main region mainly includinghollow-section fibers, and a mixed region including solid-section fibersand hollow-section fibers in a mixed state, located between thesolid-section fiber main region and the hollow-section fiber mainregion, where these regions were integrated, not separated from oneanother. The hollow-section fibers were formed of hollow linear bodieshaving a triangular rice-ball shaped hollow cross section, a hollownessof 20%, and a fiber size of 0.55 mm, and the solid-section fibers wereformed of solid linear bodies having a fiber size of 0.42 mm. Thedifference in fiber size was 0.13 mm, the total weight ratio of thesolid-section fibers was 38%, the apparent density was 0.054 g/cm³, andthe thickness of flattened surface was 48 mm.

The hollow-section fiber main region-side residual strain was 6.1%, thesolid-section fiber main region-side residual strain was 12.1%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was6.0 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 39.7 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 25.7 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.54, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 85.6 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 52.1 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.64,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 3.80, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 7.72, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 3.92,the hysteresis loss at pressurization from the hollow-section fiber mainregion side was 25.9%, the hysteresis loss at pressurization from thesolid-section fiber main region side was 25.7%, and the differencebetween the hysteresis loss at pressurization from the solid-sectionfiber main region side and the hysteresis loss at pressurization fromthe hollow-section fiber main region side was 0.2 points. The propertiesof the obtained net-like structure are shown in Table 1.

As shown in Table 1, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 30% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Example I-3

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 57.2 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in the first toseventh rows in the thickness direction at a width-direction inter-holepitch of 6 mm and a thickness-direction inter-hole pitch of 5.2 mm andsolid forming orifices having an outer size of 1 mm were zigzag-arrangedin the eighth to twelfth rows in the thickness direction at awidth-direction inter-hole pitch of 6 mm and a thickness-directioninter-hole pitch of 5.2 mm. The obtained polyester-based thermoplasticelastomer (A-1) was discharged downward from the nozzle at a spinningtemperature (melting temperature) of 240° C. at a single-hole dischargerate of 1.8 g/min for hollow holes and a single-hole discharge rate of1.1 g/min for solid holes. Cooling water was provided at a position 23cm below the nozzle face. Endless nets made of stainless steel eachhaving a width of 60 cm were placed in parallel at a spacing of 42 mm inopening width to form a pair of take-up conveyor nets so as to bepartially exposed over a water surface. Above the conveyer nets over thewater surface, the discharged filaments in a molten state were curled toform loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.74 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 110° C. hotair for 15 minutes, to obtain a net-like structure.

The obtained net-like structure was a net-like structure having asolid-section fiber main region mainly including solid-section fibers, ahollow-section fiber main region mainly including hollow-section fibers,and a mixed region including solid-section fibers and hollow-sectionfibers in a mixed state, located between the solid-section fiber mainregion and the hollow-section fiber main region, where these regionswere integrated, not separated from one another. The hollow-sectionfibers were formed of hollow linear bodies having a triangular rice-ballshaped hollow cross section, a hollowness of 23%, and a fiber size of0.81 mm, and the solid-section fibers were formed of solid linear bodieshaving a fiber size of 0.56 mm. The difference in fiber size was 0.25mm, the total weight ratio of the solid-section fibers was 30%, theapparent density was 0.044 g/cm³, and the thickness of flattened surfacewas 40 mm.

The hollow-section fiber main region-side residual strain was 6.0%, thesolid-section fiber main region-side residual strain was 4.9%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was1.1 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 18.2 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 17.7 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.03, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 37.6 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 34.9 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.08,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 5.31, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 5.59, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 0.28points, the hysteresis loss at pressurization from the hollow-sectionfiber main region side was 25.7%, the hysteresis loss at pressurizationfrom the solid-section fiber main region side was 27.1%, and thedifference between the hysteresis loss at pressurization from thesolid-section fiber main region side and the hysteresis loss atpressurization from the hollow-section fiber main region side was 1.4points. The properties of the obtained net-like structure are shown inTable 1.

As shown in Table 1, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 30% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Example I-4

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 67.6 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in the first toseventh rows in the thickness direction at a width-direction inter-holepitch of 6 mm and a thickness-direction inter-hole pitch of 5.2 mm andsolid forming orifices having an outer size of 1.2 mm werezigzag-arranged in the eighth to thirteenth rows in the thicknessdirection at a width-direction inter-hole pitch of 7 mm and athickness-direction inter-hole pitch of 6.1 mm. The obtainedpolyester-based thermoplastic elastomer (A-1) was discharged downwardfrom the nozzle at a spinning temperature (melting temperature) of 240°C. at a single-hole discharge rate of 1.1 g/min for hollow holes and asingle-hole discharge rate of 1.1 g/min for solid holes. Cooling waterwas provided at a position 28 cm below the nozzle face. Endless netsmade of stainless steel each having a width of 60 cm were placed inparallel at a spacing of 52 mm in opening width to form a pair oftake-up conveyor nets so as to be partially exposed over a watersurface. Above the conveyer nets over the water surface, the dischargedfilaments in a molten state were curled to form loops, and contactportions were fused together to form a three-dimensional net-likestructure. The net-like structure in a molten state was sandwiched atboth faces by the take-up conveyor nets, and drawn into the coolingwater at a take-up speed of 1.14 m/min, thereby solidified to beflattened at both faces in the thickness direction, then cut into apredetermined size, and dried/heated with 110° C. hot air for 15minutes, to obtain a net-like structure.

The obtained net-like structure was a net-like structure having asolid-section fiber main region mainly including solid-section fibers, ahollow-section fiber main region mainly including hollow-section fibers,and a mixed region including solid-section fibers and hollow-sectionfibers in a mixed state, located between the solid-section fiber mainregion and the hollow-section fiber main region, where these regionswere integrated, not separated from one another. The hollow-sectionfibers were formed of hollow linear bodies having a triangular rice-ballshaped hollow cross section, a hollowness of 18%, and a fiber size of0.67 mm, and the solid-section fibers were formed of solid linear bodieshaving a fiber size of 0.60 mm. The difference in fiber size was 0.07mm, the total weight ratio of the solid-section fibers was 47%, theapparent density was 0.044 g/cm³, and the thickness of flattened surfacewas 50 mm.

The hollow-section fiber main region-side residual strain was 6.6%, thesolid-section fiber main region-side residual strain was 7.0%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was0.4 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 41.2 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 37.3 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.10, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 69.0 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 65.5 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.05,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 4.51, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 4.74, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 0.23points, the hysteresis loss at pressurization from the hollow-sectionfiber main region side was 23.1%, the hysteresis loss at pressurizationfrom the solid-section fiber main region side was 23.5%, and thedifference between the hysteresis loss at pressurization from thesolid-section fiber main region side and the hysteresis loss atpressurization from the hollow-section fiber main region side was 0.4points. The properties of the obtained net-like structure are shown inTable 1.

As shown in Table 1, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 30% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Comparative Example I-R1

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 67.6 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in the first toeighth rows at a width-direction inter-hole pitch of 10 mm and athickness-direction inter-hole pitch of 7.5 mm and solid formingorifices having an outer size of 0.7 mm were zigzag-arranged in theninth to eleventh rows at a width-direction inter-hole pitch of 2.5 mmand a thickness-direction inter-hole pitch of 3.7 mm. The obtainedpolyester-based thermoplastic elastomer (A-1) was discharged downwardfrom the nozzle at a spinning temperature (melting temperature) of 240°C. at a single-hole discharge rate of 2.0 g/min for hollow holes, asingle-hole discharge rate of 0.5 g/min for solid holes, and a wholedischarge rate of 1100 g/min. Cooling water was provided at a position18 cm below the nozzle face. Endless nets made of stainless steel eachhaving a width of 60 cm were placed in parallel at a spacing of 50 mm inopening width to form a pair of take-up conveyor nets so as to bepartially exposed over a water surface. Above the conveyer nets over thewater surface, the discharged filaments in a molten state were curled toform loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.00 m/min, therebysolidified, then cut into a predetermined size, and dried/heated with110° C. hot air for 15 minutes, to obtain a net-like structure.

The obtained net-like structure was a net-like structure having asolid-section fiber main region mainly including solid-section fibersand a hollow-section fiber main region mainly including hollow-sectionfibers, where these regions were integrated, not separated from eachother. In the obtained net-like structure, the width-directioninter-hole pitch of the hollow forming orifices and the width-directioninter-hole pitch of the solid forming orifices were so different fromeach other that loops of hollow-section fibers failed to make their waysinto between loops of solid-section fibers, resulting in no presence ofa region including solid-section fibers and hollow-section fibers in amixed state to form a thickness.

The hollow-section fibers were formed of hollow linear bodies having atriangular rice-ball shaped hollow cross section, a hollowness of 28%,and a fiber size of 0.80 mm, and the solid-section fibers were formed ofsolid linear bodies having a fiber size of 0.32 mm. The difference infiber size was 0.48 mm, the total weight ratio of the solid-sectionfibers was 27%, the apparent density was 0.046 g/cm³, and the thicknessof flattened surface was 50 mm.

The hollow-section fiber main region-side residual strain was 5.3%, thesolid-section fiber main region-side residual strain was 15.6%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was10.3 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 22.7 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 21.9 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.04, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 41.1 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 40.3 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.02,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 3.80, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 3.62, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 0.18points, the hysteresis loss at pressurization from the hollow-sectionfiber main region side was 23.1%, the hysteresis loss at pressurizationfrom the solid-section fiber main region side was 23.8%, and thedifference between the hysteresis loss at pressurization from thesolid-section fiber main region side and the hysteresis loss atpressurization from the hollow-section fiber main region side was 0.7points. The properties of the obtained net-like structure are shown inTable 1.

As shown in Table 1, in the net-like structure obtained in thiscomparative example, the difference in residual strain after 750 Nconstant load repeated compression between the hollow-section fiber mainregion side and the solid-section fiber main region side was greaterthan 10 points. Therefore, the difference in compression durabilitybetween both faces was large. That is, the net-like structure obtainedin this comparative example was a net-like structure that did notsatisfy the requirements of the present invention and was large indifference in compression durability between both faces.

Comparative Example I-R2

As a nozzle, used was one having a nozzle effective face having lengthsof 1000 mm in the width direction and 31.2 mm in the thicknessdirection, on which orifices of a triple bridge hollow formative crosssection having an outer size of 3 mm and an inner size of 2.6 mm werezigzag-arranged at a width-direction inter-hole pitch of 6 mm and athickness-direction inter-hole pitch of 5.2 mm in 7 rows in thethickness direction. The obtained polyester-based thermoplasticelastomer (A-1) was discharged downward from the nozzle at a spinningtemperature (melting temperature) of 240° C. at a single-hole dischargerate of 1.5 g/min. Cooling water was provided at a position 28 cm belowthe nozzle face. Endless nets made of stainless steel each having awidth of 2000 mm were placed in parallel at a spacing of 27 mm inopening width to form a pair of take-up conveyor nets so as to bepartially exposed over a water surface. Above the conveyer nets over thewater surface, the discharged filaments in a molten state were curled toform loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.14 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 110° C. hotair for 15 minutes, to obtain a net-like structure mainly includinghollow-section fibers having a triangular rice-ball shaped crosssection. The obtained net-like structure had an apparent density of0.063 g/cm³ and a thickness of flattened surface of 25 mm, and thehollow-section fibers had a hollowness of 20% and a fiber size of 0.76mm.

Also, as a nozzle, used was one having a nozzle effective face havinglengths of 1000 mm in the width direction and 31.2 mm in the thicknessdirection, on which solid forming orifices having an outer size of 1 mmwere zigzag-arranged at a width-direction inter-hole pitch of 6 mm and athickness-direction inter-hole pitch of 5.2 mm in 7 rows in thethickness direction. The obtained polyester-based thermoplasticelastomer (A-1) was discharged downward from the nozzle at a spinningtemperature (melting temperature) of 240° C. at a single-hole dischargerate of 0.9 g/min. Cooling water was provided at a position 28 cm belowthe nozzle face. Endless nets made of stainless steel each having awidth of 2000 mm were placed in parallel at a spacing of 27 mm inopening width to form a pair of take-up conveyor nets so as to bepartially exposed over a water surface. Above the conveyer nets over thewater surface, the discharged filaments in a molten state were curled toform loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.14 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 110° C. hotair for 15 minutes, to obtain a net-like structure mainly includingsolid-section fibers. The obtained net-like structure had an apparentdensity of 0.038 g/cm³ and a thickness of flattened surface of 25 mm,and the solid-section fibers had a fiber size of 0.50 mm.

The obtained net-like structure mainly including solid-section fibersand the net-like structure mainly including solid-section fibers werestacked on each other, to form a net-like structure. The entire stackednet-like structure had an apparent density of 0.051 g/cm³ and athickness of 50 mm. The difference between the fiber size of thehollow-section fibers and the fiber size of the solid-section fibers was0.26 mm.

In the stacked net-like structure, the hollow-section fiber mainregion-side residual strain was 6.3%, the solid-section fiber mainregion-side residual strain was 17.3%, and the difference between thesolid-section fiber main region-side residual strain and thehollow-section fiber main region-side residual strain was 11.0 points.The 25% compression hardness at pressurization from the hollow-sectionfiber main region side was 45.1 N/ϕ100 mm, the 25% compression hardnessat pressurization from the solid-section fiber main region side was 32.1N/ϕ100 mm, the ratio between the 25% compression hardness atpressurization from the solid-section fiber main region side and the 25%compression hardness at pressurization from the hollow-section fibermain region side was 1.40, the 40% compression hardness atpressurization from the hollow-section fiber main region side was 75.1N/ϕ100 mm, the 40% compression hardness at pressurization from thesolid-section fiber main region side was 61.3 N/ϕ100 mm, the ratiobetween the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.23,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 4.07, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 5.99, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 1.92points, the hysteresis loss at pressurization from the hollow-sectionfiber main region side was 23.7%, the hysteresis loss at pressurizationfrom the solid-section fiber main region side was 26.2%, and thedifference between the hysteresis loss at pressurization from thesolid-section fiber main region side and the hysteresis loss atpressurization from the hollow-section fiber main region side was 2.5points. The properties of the obtained net-like structure are shown inTable 1.

As shown in Table 1, in the net-like structure obtained in thiscomparative example, the difference in residual strain after 750 Nconstant load repeated compression between the hollow-section fiber mainregion side and the solid-section fiber main region side was greaterthan 10 points. Therefore, the difference in compression durabilitybetween both faces was large. That is, the net-like structure obtainedin this comparative example was a net-like structure that did notsatisfy the requirements of the present invention and was large indifference in compression durability between both faces.

TABLE 1 Compar- Compar- Exam- Exam- ative ative Example Example ple pleExample Example I-1 I-2 I-3 I-4 I-R1 I-R2 Thermoplastic elastomer (A-1)(A-1) (A-1) (A-1) (A-1) (A-1) Spinning Temperature (° C.) 240 240 240240 240 240   Single-hole discharge Hollow holes (g/min) 1.5 1.5 1.8 1.12.0  1.5 rate Solid holes (g/min) 0.9 0.9 1.1 1.1 0.5  0.9 Nozzleface-cooling water distance (cm) 28 32 23 28 18 28   Take-up speed(m/min) 1.14 1.14 1.74 1.14 1.00  1.14 Fiber size Hollow-section fibers(mm) 0.76 0.55 0.81 0.67 0.80  0.76 Solid-section fibers (mm) 0.50 0.420.56 0.60 0.32  0.50 Difference in fiber size (mm) 0.26 0.13 0.25 0.070.48  0.26 Hollowness of hollow-section fibers (%) 20 20 23 18 28 20  Total weight ratio of solid-section fibers (%) 38 38 30 47 27 — Apparentdensity (g/cm³) 0.055 0.054 0.044 0.044 0.046    0.051*¹ Thickness (mm)50 48 40 50 50  50*¹ Residual strain after Hollow-section fiber mainregion side (%) 6.7 6.1 6.0 6.6 5.3  6.3 750N constant loadSolid-section fiber main region side (%) 5.7 12.1 4.9 7.0 15.6 17.3repeated compression Difference between two sides (Point) 1.0 6.0 1.10.4 10.3 11.0 25% compression Hollow-section fiber main region side(N/ϕ100 mm) 45.1 39.7 18.2 41.2 22.7 45.1 hardness Solid-section fibermain region side (N/ϕ100 mm) 32.1 25.7 17.7 37.3 21.9 32.1 Ratio betweentwo sides (—) 1.40 1.54 1.03 1.10 1.04  1.40 40% compressionHollow-section fiber main region side (N/ϕ100 mm) 75.1 85.6 37.6 69.041.1 75.1 hardness Solid-section fiber main region side (N/ϕ100 mm) 61.352.1 34.9 65.5 40.3 61.3 Ratio between two sides (—) 1.23 1.64 1.08 1.051.02  1.23 Compression Hollow-section fiber main region side (—) 4.073.80 5.31 4.51 3.80  4.07 deflection Solid-section fiber main regionside (—) 5.99 7.72 5.59 4.74 3.62  5.99 coefficient Difference betweentwo sides (—) 1.92 3.92 0.28 0.23 0.18  1.92 Hysteresis lossHollow-section fiber main region side (%) 23.7 25.9 25.7 23.1 23.1 23.7Solid-section fiber main region side (%) 26.2 25.7 27.1 23.5 23.8 26.2Difference between two sides (Point) 2.5 0.2 1.4 0.4 0.7  2.5 *¹Value inthe state of stacking of 2 net-like structures

Example II-1

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 67.6 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in the first toseventh rows in the thickness direction at a width-direction inter-holepitch of 6 mm and a thickness-direction inter-hole pitch of 5.2 mm andsolid forming orifices having an outer size of 1 mm were zigzag-arrangedin the eighth to fourteenth rows in the thickness direction at awidth-direction inter-hole pitch of 6 mm and a thickness-directioninter-hole pitch of 5.2 mm. INFUSE D9530.05 (manufactured by DowChemical Company), a multi-block copolymer constituted ofethylene-α-olefin, 100 wt %, was used as a polyolefin-basedthermoplastic elastomer (B-1), discharged downward from the nozzle at aspinning temperature (melting temperature) of 240° C. at a single-holedischarge rate of 1.8 g/min for hollow holes and a single-hole dischargerate of 1.1 g/min for solid holes. Cooling water was provided at aposition 30 cm below the nozzle face. Endless nets made of stainlesssteel each having a width of 60 cm were placed in parallel at a spacingof 50 mm in opening width to form a pair of take-up conveyor nets so asto be partially exposed over a water surface. Above the conveyer netsover the water surface, the discharged filaments in a molten state werecurled to form loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.43 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 70° C. hot airfor 15 minutes, to obtain a net-like structure.

The obtained net-like structure was a net-like structure having asolid-section fiber main region mainly including solid-section fibers, ahollow-section fiber main region mainly including hollow-section fibers,and a mixed region including solid-section fibers and hollow-sectionfibers in a mixed state, located between the solid-section fiber mainregion and the hollow-section fiber main region, where these regionswere integrated, not separated from one another. The hollow-sectionfibers were formed of hollow linear bodies having a triangular rice-ballshaped hollow cross section, a hollowness of 30%, and a fiber size of1.13 mm, and the solid-section fibers were formed of solid linear bodieshaving a fiber size of 0.52 mm. The difference in fiber size was 0.61mm, the total weight ratio of the solid-section fibers was 37%, theapparent density was 0.043 g/cm³, and the thickness of flattened surfacewas 45 mm.

The hollow-section fiber main region-side residual strain was 11.4%, thesolid-section fiber main region-side residual strain was 13.5%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was2.1 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 11.0 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 6.2 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.77, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 22.2 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 19.1 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.16,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 4.63, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 7.59, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 2.96,the hysteresis loss at pressurization from the hollow-section fiber mainregion side was 42.6%, the hysteresis loss at pressurization from thesolid-section fiber main region side was 44.8%, and the differencebetween the hysteresis loss at pressurization from the solid-sectionfiber main region side and the hysteresis loss at pressurization fromthe hollow-section fiber main region side was 2.2 points. The propertiesof the obtained net-like structure are shown in Table 2.

As shown in Table 2, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 60% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Example II-2

A net-like structure was obtained in the same manner as in Example II-1except that cooling water was provided at a position 38 cm below thenozzle face. The obtained net-like structure was a net-like structurehaving a solid-section fiber main region mainly including solid-sectionfibers, a hollow-section fiber main region mainly includinghollow-section fibers, and a mixed region including solid-section fibersand hollow-section fibers in a mixed state, located between thesolid-section fiber main region and the hollow-section fiber mainregion, where these regions were integrated, not separated from oneanother. The hollow-section fibers were formed of hollow linear bodieshaving a triangular rice-ball shaped hollow cross section, a hollownessof 28%, and a fiber size of 1.00 mm, and the solid-section fibers wereformed of solid linear bodies having a fiber size of 0.47 mm. Thedifference in fiber size was 0.53 mm, the total weight ratio of thesolid-section fibers was 37%, the apparent density was 0.045 g/cm³, andthe thickness of flattened surface was 43 mm.

The hollow-section fiber main region-side residual strain was 11.6%, thesolid-section fiber main region-side residual strain was 13.0%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was1.4 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 15.3 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 9.7 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.58, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 28.5 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 23.7 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.20,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 4.29, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 6.30, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 2.01,the hysteresis loss at pressurization from the hollow-section fiber mainregion side was 42.5%, the hysteresis loss at pressurization from thesolid-section fiber main region side was 46.2%, and the differencebetween the hysteresis loss at pressurization from the solid-sectionfiber main region side and the hysteresis loss at pressurization fromthe hollow-section fiber main region side was 3.7 points. The propertiesof the obtained net-like structure are shown in Table 2.

As shown in Table 2, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 60% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Example II-3

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 67.6 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in the first toseventh rows in the thickness direction at a width-direction inter-holepitch of 6 mm and a thickness-direction inter-hole pitch of 5.2 mm andsolid forming orifices having an outer size of 1 mm were zigzag-arrangedin the eighth to fourteenth rows in the thickness direction at awidth-direction inter-hole pitch of 6 mm and a thickness-directioninter-hole pitch of 5.2 mm. INFUSE D9530.05 (manufactured by DowChemical Company), a multi-block copolymer constituted ofethylene-α-olefin, 100 wt %, was used as a polyolefin-basedthermoplastic elastomer, discharged downward from the nozzle at aspinning temperature (melting temperature) of 240° C. at a single-holedischarge rate of 1.8 g/min for hollow holes and a single-hole dischargerate of 1.1 g/min for solid holes. Cooling water was provided at aposition 30 cm below the nozzle face. Endless nets made of stainlesssteel each having a width of 60 cm were placed in parallel at a spacingof 40 mm in opening width to form a pair of take-up conveyor nets so asto be partially exposed over a water surface. Above the conveyer netsover the water surface, the discharged filaments in a molten state werecurled to form loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.84 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 70° C. hot airfor 15 minutes, to obtain a net-like structure.

The obtained net-like structure was a net-like structure having asolid-section fiber main region mainly including solid-section fibers, ahollow-section fiber main region mainly including hollow-section fibers,and a mixed region including solid-section fibers and hollow-sectionfibers in a mixed state, located between the solid-section fiber mainregion and the hollow-section fiber main region, where these regionswere integrated, not separated from one another. The hollow-sectionfibers were formed of hollow linear bodies having a triangular rice-ballshaped hollow cross section, a hollowness of 29%, and a fiber size of1.14 mm, and the solid-section fibers were formed of solid linear bodieshaving a fiber size of 0.57 mm. The difference in fiber size was 0.57mm, the total weight ratio of the solid-section fibers was 37%, theapparent density was 0.052 g/cm³, and the thickness of flattened surfacewas 32 mm.

The hollow-section fiber main region-side residual strain was 12.2%, thesolid-section fiber main region-side residual strain was 13.9%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was1.7 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 7.7 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 6.5 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.18, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 19.3 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 16.8 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.15,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 9.44, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 9.61, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 0.17,the hysteresis loss at pressurization from the hollow-section fiber mainregion side was 43.4%, the hysteresis loss at pressurization from thesolid-section fiber main region side was 47.2%, and the differencebetween the hysteresis loss at pressurization from the solid-sectionfiber main region side and the hysteresis loss at pressurization fromthe hollow-section fiber main region side was 3.8 points. The propertiesof the obtained net-like structure are shown in Table 2.

As shown in Table 2, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 60% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Example II-4

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 77.9 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in the first totenth rows in the thickness direction at a width-direction inter-holepitch of 6 mm and a thickness-direction inter-hole pitch of 5.2 mm andsolid forming orifices having an outer size of 1 mm were zigzag-arrangedin the eleventh to sixteenth rows in the thickness direction at awidth-direction inter-hole pitch of 6 mm and a thickness-directioninter-hole pitch of 5.2 mm. DOWLEX 2035G (manufactured by Dow ChemicalCompany), a random block copolymer constituted of ethylene-α-olefin, 100wt %, was used as a polyolefin-based thermoplastic elastomer (B-2),discharged downward from the nozzle at a spinning temperature (meltingtemperature) of 230° C. at a single-hole discharge rate of 1.3 g/min forhollow holes and a single-hole discharge rate of 0.8 g/min for solidholes. Cooling water was provided at a position 32 cm below the nozzleface. Endless nets made of stainless steel each having a width of 60 cmwere placed in parallel at a spacing of 60 mm in opening width to form apair of take-up conveyor nets so as to be partially exposed over a watersurface. Above the conveyer nets over the water surface, the dischargedfilaments in a molten state were curled to form loops, and contactportions were fused together to form a three-dimensional net-likestructure. The net-like structure in a molten state was sandwiched atboth faces by the take-up conveyor nets, and drawn into the coolingwater at a take-up speed of 1.54 m/min, thereby solidified to beflattened at both faces in the thickness direction, then cut into apredetermined size, and dried/heated with 70° C. hot air for 15 minutes,to obtain a net-like structure.

The obtained net-like structure was a net-like structure having asolid-section fiber main region mainly including solid-section fibers, ahollow-section fiber main region mainly including hollow-section fibers,and a mixed region including solid-section fibers and hollow-sectionfibers in a mixed state, located between the solid-section fiber mainregion and the hollow-section fiber main region, where these regionswere integrated, not separated from one another. The hollow-sectionfibers were formed of hollow linear bodies having a triangular rice-ballshaped hollow cross section, a hollowness of 33%, and a fiber size of0.88 mm, and the solid-section fibers were formed of solid linear bodieshaving a fiber size of 0.49 mm. The difference in fiber size was 0.39mm, the total weight ratio of the solid-section fibers was 38%, theapparent density was 0.032 g/cm³, and the thickness of flattened surfacewas 56 mm.

The hollow-section fiber main region-side residual strain was 15.1%, thesolid-section fiber main region-side residual strain was 15.5%, and thedifference between the solid-section fiber main region-side residualstrain and the hollow-section fiber main region-side residual strain was0.4 points. The 25% compression hardness at pressurization from thehollow-section fiber main region side was 23.0 N/ϕ100 mm, the 25%compression hardness at pressurization from the solid-section fiber mainregion side was 17.0 N/ϕ100 mm, the ratio between the 25% compressionhardness at pressurization from the solid-section fiber main region sideand the 25% compression hardness at pressurization from thehollow-section fiber main region side was 1.35, the 40% compressionhardness at pressurization from the hollow-section fiber main regionside was 40.4 N/ϕ100 mm, the 40% compression hardness at pressurizationfrom the solid-section fiber main region side was 36.3 N/ϕ100 mm, theratio between the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.11,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 3.50, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 5.01, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 1.51,the hysteresis loss at pressurization from the hollow-section fiber mainregion side was 39.7%, the hysteresis loss at pressurization from thesolid-section fiber main region side was 43.6%, and the differencebetween the hysteresis loss at pressurization from the solid-sectionfiber main region side and the hysteresis loss at pressurization fromthe hollow-section fiber main region side was 3.9 points. The propertiesof the obtained net-like structure are shown in Table 2.

As shown in Table 2, in the net-like structure obtained in this example,the residual strains after 750 N constant load repeated compression onthe hollow-section fiber main region side and the solid-section fibermain region side were less than or equal to 20% with the differencetherebetween being less than or equal to 10 points, the difference incompression deflection coefficient between the hollow-section fiber mainregion side and the solid-section fiber main region side was less thanor equal to 5, and the hysteresis losses on the hollow-section fibermain region side and the solid-section fiber main region side were lessthan or equal to 60% with the difference therebetween being less than orequal to 5 points, which were all small. Therefore, the difference incompression durability between both faces was small. Also, in thenet-like structure obtained in this example, the ratio in 25%compression hardness between the hollow-section fiber main region sideand the solid-section fiber main region side was greater than or equalto 1.03, and the ratio in 40% compression hardness between thehollow-section fiber main region side and the solid-section fiber mainregion side was greater than or equal to 1.05, which were both large.Therefore, cushioning performance different between both faces wasimparted. That is, the net-like structure obtained in this example wasan excellent net-like structure that satisfied the requirements of thepresent invention, was small in difference in compression durabilitybetween both faces, and was provided with cushioning performancedifferent between both faces.

Comparative Example II-R1

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 31.2 mm in the thickness direction,on which triple bridge hollow forming orifices having an outer size of 3mm and an inner size of 2.6 mm were zigzag-arranged in 7 rows in thethickness direction at a width-direction inter-hole pitch of 6 mm and athickness-direction inter-hole pitch of 5.2 mm. INFUSE D9530.05(manufactured by Dow Chemical Company), a multi-block copolymerconstituted of ethylene-α-olefin, 100 wt %, was used as apolyolefin-based thermoplastic elastomer, discharged downward from thenozzle at a spinning temperature (melting temperature) of 240° C. at asingle-hole discharge rate of 1.8 g/min. Cooling water was provided at aposition 38 cm below the nozzle face. Endless nets made of stainlesssteel each having a width of 60 cm were placed in parallel at a spacingof 30 mm in opening width to form a pair of take-up conveyor nets so asto be partially exposed over a water surface. Above the conveyer netsover the water surface, the discharged filaments in a molten state werecurled to form loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.43 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 70° C. hot airfor 15 minutes, to obtain a net-like structure mainly includinghollow-section fibers having a triangular rice-ball shaped crosssection. The obtained net-like structure had an apparent density of0.048 g/cm³ and a thickness of flattened surface of 25 mm, and thehollow-section fibers had a hollowness of 30% and a fiber size of 1.00mm.

As a nozzle, used was one having a nozzle effective face having lengthsof 50 cm in the width direction and 31.2 mm in the thickness direction,on which solid forming orifices having an outer size of 1 mm werezigzag-arranged in 7 rows in the thickness direction at awidth-direction inter-hole pitch of 6 mm and a thickness-directioninter-hole pitch of 5.2 mm. INFUSE D9530.05 (manufactured by DowChemical Company), a multi-block copolymer constituted ofethylene-α-olefin, 100 wt %, was used as a polyolefin-basedthermoplastic elastomer, discharged downward from the nozzle at aspinning temperature (melting temperature) of 240° C. at a single-holedischarge rate of 1.1 g/min. Cooling water was provided at a position 38cm below the nozzle face. Endless nets made of stainless steel eachhaving a width of 60 cm were placed in parallel at a spacing of 25 mm inopening width to form a pair of take-up conveyor nets so as to bepartially exposed over a water surface. Above the conveyer nets over thewater surface, the discharged filaments in a molten state were curled toform loops, and contact portions were fused together to form athree-dimensional net-like structure. The net-like structure in a moltenstate was sandwiched at both faces by the take-up conveyor nets, anddrawn into the cooling water at a take-up speed of 1.43 m/min, therebysolidified to be flattened at both faces in the thickness direction,then cut into a predetermined size, and dried/heated with 70° C. hot airfor 15 minutes, to obtain a net-like structure mainly includingsolid-section fibers. The obtained net-like structure had an apparentdensity of 0.037 g/cm³ and a thickness of flattened surface of 20 mm,and the solid-section fibers had a fiber size of 0.45 mm.

The obtained net-like structure mainly including solid-section fibersand the net-like structure mainly including solid-section fibers werestacked on each other, to form a net-like structure. The entire stackednet-like structure had an apparent density of 0.043 g/cm³ and athickness of 45 mm. The difference between the fiber size of thehollow-section fibers and the fiber size of the solid-section fibers was0.55 mm.

In the stacked net-like structure, the hollow-section fiber mainregion-side residual strain was 11.2%, the solid-section fiber mainregion-side residual strain was 28.5%, and the difference between thesolid-section fiber main region-side residual strain and thehollow-section fiber main region-side residual strain was 17.3 points.The 25% compression hardness at pressurization from the hollow-sectionfiber main region side was 8.8 N/ϕ100 mm, the 25% compression hardnessat pressurization from the solid-section fiber main region side was 4.4N/ϕ100 mm, the ratio between the 25% compression hardness atpressurization from the solid-section fiber main region side and the 25%compression hardness at pressurization from the hollow-section fibermain region side was 2.00, the 40% compression hardness atpressurization from the hollow-section fiber main region side was 20.8N/ϕ100 mm, the 40% compression hardness at pressurization from thesolid-section fiber main region side was 13.4 N/ϕ100 mm, the ratiobetween the 40% compression hardness at pressurization from thesolid-section fiber main region side and the 40% compression hardness atpressurization from the hollow-section fiber main region side was 1.55,the compression deflection coefficient at pressurization from thehollow-section fiber main region side was 7.87, the compressiondeflection coefficient at pressurization from the solid-section fibermain region side was 11.8, the difference between the compressiondeflection coefficient at pressurization from the solid-section fibermain region side and the compression deflection coefficient atpressurization from the hollow-section fiber main region side was 3.93points, the hysteresis loss at pressurization from the hollow-sectionfiber main region side was 47.4%, the hysteresis loss at pressurizationfrom the solid-section fiber main region side was 48.1%, and thedifference between the hysteresis loss at pressurization from thesolid-section fiber main region side and the hysteresis loss atpressurization from the hollow-section fiber main region side was 0.7points. The properties of the obtained net-like structure are shown inTable 2.

As shown in Table 2, in the net-like structure obtained in thiscomparative example, after repeated compression with a constant load of750 N on the hollow-section fiber main region side and the solid-sectionfiber main region side, the residual strain on the solid-section fibermain region side was greater than 20%, and the difference between theresidual strain on the solid-section fiber main region side and theresidual strain on the hollow-section fiber main region side was greaterthan 10 points. Therefore, the difference in compression durabilitybetween both faces was large. That is, the net-like structure obtainedin this comparative example was a net-like structure that did notsatisfy the requirements of the present invention and was large indifference in compression durability between both faces.

TABLE 2 Comparative Example Example Example Example Example II-1 II-2II-3 II-4 II-R1 Thermoplastic elastomer (B-1) (B-1) (B-1) (B-2) (B-1)Spinning Temperature (° C.) 240 240 240 230 240   Single-hole dischargeHollow holes (g/min) 1.8 1.8 1.8 1.3  1.8 rate Solid holes (g/min) 1.11.1 1.1 0.8  1.1 Nozzle face-cooling water distance (cm) 30 38 30 3238   Take-up speed (m/min) 1.43 1.43 1.84 1.54  1.43 Fiber sizeHollow-section fibers (mm) 1.13 1.00 1.14 0.88  1.00 Solid-sectionfibers (mm) 0.52 0.47 0.57 0.49  0.45 Difference in fiber size (mm) 0.610.53 0.57 0.39  0.55 Hollowness of hollow-section fibers (%) 30 28 29 3330   Total weight ratio of solid-section fibers (%) 37 37 37 38 —Apparent density (g/cm³) 0.043 0.045 0.052 0.032    0.043*¹ Thickness(mm) 45 43 32 56  45*¹ Residual strain after Hollow-section fiber mainregion side (%) 11.4 11.6 12.2 15.1 11.2 750N constant loadSolid-section fiber main region side (%) 13.5 13.0 13.9 15.5 28.5repeated compression Difference between two sides (Point) 2.1 1.4 1.70.4 17.3 25% compression Hollow-section fiber main region side (N/ϕ100mm) 11.0 15.3 7.7 23.0  8.8 hardness Solid-section fiber main regionside (N/ϕ100 mm) 6.2 9.7 6.5 17.0  4.4 Ratio between two sides (—) 1.771.58 1.18 1.35  2.00 40% compression Hollow-section fiber main regionside (N/ϕ100 mm) 22.2 28.5 19.3 40.4 20.8 hardness Solid-section fibermain region side (N/ϕ100 mm) 19.1 23.7 16.8 36.3 13.4 Ratio between twosides (—) 1.16 1.20 1.15 1.11  1.55 Compression deflectionHollow-section fiber main region side (—) 4.63 4.29 9.44  3.50  7.87coefficient Solid-section fiber main region side (—) 7.59 6.30 9.61 5.0111.8 Difference between two sides (—) 2.96 2.01 0.17 1.51  3.93Hysteresis loss Hollow-section fiber main region side (%) 42.6 42.5 43.439.7 47.4 Solid-section fiber main region side (%) 44.8 46.2 47.2 43.648.1 Difference between two sides (Point) 2.2 3.7 3.8 3.9  0.7 *¹Valuein the state of stacking of 2 net-like structures

It is to be understood that the embodiments and examples disclosedherein are illustrative and not restrictive in every respect. The scopeof the present invention should be defined by the appended claims ratherthan by the description detailed above, and all changes that fall withinthe meaning and scope equivalent to the claims are intended to beembraced by the claims.

INDUSTRIAL APPLICABILITY

The net-like structure of the present invention has been obtained byimproving the problems, which have been problems of conventional complexmolded products made of a net-like structure and another net-likestructure, a net-like structure and hard cotton, a net-like structureand urethane, etc., that the compression durability is different betweenthe case of use from one of two faces and the case of use from the otherface, that the manufacturing cost is high, that the hardness changeswith the amount of an adhesive applied if applied, causing a feeling ofstrangeness, and that recycling is cumbersome, without impairing thecomfort to sit on and air permeability conventionally possessed by thenet-like structure. Therefore, the present invention can provide anet-like structure having high added value by imparting cushioningfeeling different between both faces, which is suitable for cushionmaterials used for office chairs, furniture, sofas, beddings such asbeds, seats for vehicles such as trains, automobiles, two-wheeledvehicles, baby buggies, and child safety seats, shock-absorbing matssuch as floor mats and members for preventing collision and nipping,etc. The present invention therefore greatly contributes to theindustrial world.

1. A net-like structure having a three-dimensional random loop bondedstructure constituted of a thermoplastic elastomer continuous linearbody that is either a polyester-based thermoplastic elastomer continuouslinear body or a polyolefin-based thermoplastic elastomer continuouslinear body having a fiber size of greater than or equal to 0.1 mm andless than or equal to 3.0 mm, wherein the net-like structure has, in athickness direction of said net-like structure, a solid-section fibermain region mainly including fibers having a solid cross section, ahollow-section fiber main region mainly including fibers having a hollowcross section, and a mixed region including fibers having a solid crosssection and fibers having a hollow cross section in a mixed state,located between said solid-section fiber main region and saidhollow-section fiber main region, both solid-section fiber mainregion-side residual strain after 750 N constant load repeatedcompression at pressurization from the side of said solid-section fibermain region of said net-like structure and hollow-section fiber mainregion-side residual strain after 750 N constant load repeatedcompression at pressurization from the side of said hollow-section fibermain region of said net-like structure are less than or equal to 20%,and a difference between said solid-section fiber main region-sideresidual strain and said hollow-section fiber main region-side residualstrain is less than or equal to 10 points.
 2. The net-like structureaccording to claim 1, wherein an apparent density is greater than orequal to 0.005 g/cm³ and less than or equal to 0.20 g/cm³.
 3. Thenet-like structure according to claim 1, wherein said fibers having ahollow cross section have a fiber size greater than said fibers having asolid cross section, and a difference in fiber size between said fibershaving a solid cross section and said fibers having a hollow crosssection is greater than or equal to 0.07 mm.
 4. The net-like structureaccording to claim 1, wherein a ratio between 25% compression hardnessat pressurization from the side of said solid-section fiber main regionand 25% compression hardness at pressurization from the side of saidhollow-section fiber main region is greater than or equal to 1.03. 5.The net-like structure according to claim 1, wherein a ratio between 40%compression hardness at pressurization from the side of saidsolid-section fiber main region and 40% compression hardness atpressurization from the side of said hollow-section fiber main region isgreater than or equal to 1.05.
 6. The net-like structure according toclaim 1, wherein a difference between a compression deflectioncoefficient at pressurization from the side of said solid-section fibermain region and a compression deflection coefficient at pressurizationfrom the side of said hollow-section fiber main region is less than orequal to
 5. 7. The net-like structure according to claim 1, wherein adifference between a hysteresis loss at pressurization from the side ofsaid solid-section fiber main region and a hysteresis loss atpressurization from the side of said hollow-section fiber main region isless than or equal to 5 points.
 8. The net-like structure according toclaim 1, wherein said thermoplastic elastomer continuous linear body issaid polyester-based thermoplastic elastomer continuous linear body, andboth a hysteresis loss at pressurization from the side of saidsolid-section fiber main region and a hysteresis loss at pressurizationfrom the side of said hollow-section fiber main region are less than orequal to 30%.
 9. The net-like structure according to claim 1, whereinsaid thermoplastic elastomer continuous linear body is saidpolyolefin-based thermoplastic elastomer continuous linear body, andboth a hysteresis loss at pressurization from the side of saidsolid-section fiber main region and a hysteresis loss at pressurizationfrom the side of said hollow-section fiber main region are less than orequal to 60%.
 10. A cushion material including the net-like structureaccording to claim 1 inside the cushion, wherein the cushion material isusable reversibly.